There's some good news and some bad news.
The bad news is that it's close enough to 1e that I had trouble finding the places where the core rules definitely differed (admittedly, it's been a while since I looked at 1e). The things that immediately jumped out at me were:
- The way Intel Points works has changed a fair bit.
- Trade fleets now operate in a single system, less work plotting paths and less potential exploitability of convoy escorts.
- Constructing ships now takes time and there are a limited number of construction slots on shipyards. Civilian fleets are exempt from construction time and slots (they're just contractors).
- Colony fleets don't have to pick up census in order to establish a new colony (but get a bonus if they do).
- I think the Reinforcements Pool in space combat has changed but I'm not really sure? This is also true of the system morale changes table.
- Leftover damage changed in space combat, in a way which produces more satisfactory outcomes but also requires a little more bookkeeping.
(Also, the editing isn't great - there are some sections that are organized poorly, and the phrase "imperial thrown world" drives me mad)
The good news is that you can probably still use most of the Menagerie and the Moderator's Companion material from 1e in 2e.
The actual good news is that there are some new and improved optional rules (though the WMD rules seem to have gone missing), the new unit design system looks pretty good, and there's a lot more advice for moderators on setting starting conditions and generally making the game work. The provided scenarios have been improved; starting force values are higher (meaning you can skip or reduce the boring buildup phase of the early game) and there are more victory conditions across the board. The changes to Barbarians at the Gates are particularly well-done. The new starmaps are really aesthetically pleasing, too.
At the end of the day, though, VBAM2 has failed to escape 1e's "World War II in spaaaace" nature. Its economics are solidly Industrial Era, its navies are along battleships-and-carriers lines, and the whole game structure is of War for Vast Territorial Conquest (which van Creveld has argued in both Rise and Decline of the State and The Transformation of War to be obsolete in the Age of the Nuke). Admittedly space changes that dynamic some, but if you're willing to allow ships with stealth and FTL (as these rules do), second-strike capability with nukes or grey goo bombs or whatever is possible and a MAD situation seems likely to follow logically. Overall it feels rather like a Pacific Theatre island-hopping game with some colonization rules and "FUTURE" stamped in front of it in big red letters. The 2e draft materials that I recall reading back when bore some promise in this regard - more custom tech, more interesting things like planet destroyers and Homeworld-style nomad fleets, stuff like that. But as a consequence of sticking close to 1e, 2e has failed in this regard.
It's a pity, too, because computers are generally inadequate for science fiction and fantasy grand strategy games. Computers handle historical games well because they're tightly scoped with limited possible deviation, but in a scifi/fantasy grand strategy game, breaking the rules is sort of the point. If I can't build ringworlds and planetary disassemblers and industrial-scale cloning vats and targeted bioweapons... why bother? You could write all these things into the rules, but it'd be a bloated mess. My understanding is that this is sort of what happened to the 2e I was hoping for. At the end of the day, you have to have plenty of human discretion in the loop to run a game like that; codifying infinite diversity is self-defeating. But the assumptions in VBAM's core rules, things like "population is a meaningful factor in determining production", make it kinda hard to use as a basis for exploring interesting universes.
In conclusion: It is difficult to compare the work to the author's intent, because that intent clearly changed substantially over the course of development. Speaking personally, I will probably never play this game. It is an upgrade from 1e, but not in any of the areas that were keeping us from playing 1e. It'd be a fine computer game, but there're still too many rules and too much paperwork for any of the potential players I know to be interested in playing it manually, and once you automate it you lose the flexibility to do interesting things (which the system already doesn't support without some elbow grease).