This is not a simulationist game. At all. It has neither the engineering grunge nor history-simulating character generation of Traveller, nor does it go into the sort of economic considerations that ACKS does (which would, admittedly, be a lot harder in a science fiction setting).
Does it look like a fine, fun, fast-paced, deadly fusion of TSR D&D and Traveller? Certainly. But it is OSR of the Golden Age, rather than the Silver Age which I favor.
There are some rough edges on the merger, too. I'm not really sure how I feel about ascending D&D-style HP in science fiction, for example, and I don't think I like what a strong skill system like the one SWN borrows from Traveller does to the assumed "permitted unless implausible / apply gear, solve problem" competence of the OSR D&D character (as exemplified by the application of the 10' pole to the trapfinding problem - this does come up in the GMing chapter, but I'd rather it be front and center in Using Skills). I also quite dislike the max-skill-value-by-level rules, which mean that you can't have low-level "civilian" masters of a skill unless you're willing to have NPCs play by different rules from PCs (which is a valid approach, but not one I favor because inevitably they're going to recruit the guy who breaks the rules as a henchman and then someone will die and try to play him as a PC and then things can get messy. I prefer for PC-species to be more consistently modeled).
- Interesting psi system. The psi healing rules in particular lend themselves nicely to long adventuring days interspersed infrequently among weeks of downtime, which is a nice inversion of the standard approach to resource management. The ability to master powers for unlimited use at the cost of versatility also handily differentiates this system from traditional magic systems, as does the "one spell per school per level" thing, which limits psychic versatility. Well done.
- Gear - conveniently straightforward encumbrance system. Descending AC, though, of which I am not the biggest fan. Firearm vs. melee damage is always a fun topic, especially with abstract HP. Sniper rifle save-or-dies. Revenant Wiring is rad. Starship construction is very straightforward - pick hull, apply upgrades (which cost money, tonnage, power, and hardpoints), apply modifiers to stat-line, sum costs, done. None of this "distributed hull or semi-streamlined?" business. Starship weapons are a bit more exotic than Traveller's ("Reaper Battery" vs "Particle Beam") and the general feel from the gear lists is a bit softer sci-fi. Sandcasters no longer useful for scattering lasers - just anti-fighter weapons.
- Systems / Combat - PC exceptionalism in initiative betrays the narrative focus of the system. I kinda like the saving throw categories, though - clearer cut than OD&D's. Radiation is not as permanent as in Traveller, though xenoallergies are a nice touch. I would totally graft ACKS' death and dismemberment chart onto these injury rules, rather than "dead at 0". Natural healing is pretty quick. Has the "reroll total HD at each level and take best of previous HP or newly-rolled HP" rule, which means you're not going to have the fighter whose primary character trait is "glassjaw" unless he's got bad Con. Starship detection rules look pretty good, though I'm not sure we've ever actually played Traveller's sensors by rules-as-written. SWN treats starship ranges much less mathematically than Trav.
- GMing - Fairly good but relatively basic sandboxing advice. Also good advice on handling a skill system in the OSR style, though I'd've rather seen it up nearer the skill section, in the player chapters - part of the problem with skill systems, from my point of view, is that players whose characters have skills on their character sheet tend to use them as their first resort, rather than seeking clever ideas. No economic system to speak of in the core book; put off to Suns of Gold.
- World Generation - all of the rolls for atmo and temperature and whatnot are unlinked, rather than linked like Trav's. I do like having a biosphere roll, though, as well as a chance of an alien population rather than humans. No government roll, which saves the lookup on the Table of Curiously Quaint Future Governments That I Can Never Remember. World tags serve the same purpose as the Cultural Differences table in MongTrav, but better (you're going to get more / better adventure seeds, and less Unusual Customs, which can be entertaining).
- Factions - I skimmed this chapter on the most recent pass. The rules seem reasonable, but they're not really something I feel like I need. If I'm just trying to generate news bullets, I can get away with less, and if my PCs are leading the Rebel Alliance against the Empire, I'd rather use something closer to ACKS' degree of detail. My players, of course, might disagree, and therein I expect this subsystem might find its intended use. Campaign-style wargames aren't everyone's cup of tea, I suppose. I guess the takeaway here is that these are domains designed to keep the focus tighly on the PCs even into high levels, whereas in ACKS the individual PC becomes less mechanically significant relative to his domain as level increases (there's been some discussion on the fora to the effect that "at really high levels, mass combat-relevant proficiencies (feats) are probably the most influential mechanical bits of PCs. When you're fighting at legion-scale, your class or spellcasting abilities don't matter much."). I expect I'd find much the same 'tightly-PC-focused domains' in An Echo Resounding.
- Adventure Creation - mostly skipped. Average rewards per adventure and a Calibrating Combat sidebar again show narrativist leanings. Good d% table of hooks, in a mad-lib form similar to the adventure templates in Suns of Gold, though.
- Aliens - I very much like the lenses here; I think it nicely captures Nivenesque alien psychology. I also like how "Party-Butchering Hell Beast" is an entry on the alien critter base chasis table. Much less ecologically interested than Traveller, though - more like Star Wars-style wildlife. I am also amused that the planet Kant orbits around star Schopenhauer, but I suppose Kantian Javelin Lizard rolls off the tongue better than Schopenhauerian anything, really. Pirate captains are only 4HD?
- Robots and Mechs - the AI rules look like they'd make for rather playable PCs! It's basically point-buy for mental ability scores, skills, save and to-hit progression, and ability to use various hulls, ranging from a box equipped with a speaker up to a 4m tall four-armed killbot with an anti-vehicle laser. Unfortunately, no rules for ship's AIs. The mech rules seem reasonablish for a mech-centric game, but as with starship construction the rules are not very engineery.
- Societies - I enjoyed this chapter, and would steal from it for fantasy games. The structure of "founded for X reason, had Y government which was altered by catastrophy or time to Z government, two or three interesting traits A, B, and C, and now there's internal social conflict D" seems like a good one-paragraph need-to-know actionable summary.
- Design Notes - Accurate documentation of design decisions; good insights into other chapters. Some of my notes are derived from them. Wish we saw more chapters like this one in other RPGs. Would also have done well nearer the beginning of the book - design decisions up front!
- GM Resources - good name tables, may steal. The corporation name generation's entertaining too. Could see borrowing the Quick Heresies stuff for Midnight.
(Introspective moment - why do I prefer simulationism to narrativism so strongly, anyway? A topic for another post at a more reasonable hour, methinks)