Hopefully this isn't disallowed. 
I figured if "Let's Play" videos are allowed, so too could be a simple post. If this isn't kosher, my apologies.
Just some tasty tidbits (some differences between GC2 and GC3, not bugs or glitches, but currently implemented though, of course, subject to change or removal) for those who haven't bought in as Elite Founders that I (as an Elite Founder) have found while trying out the GC3 alpha.
If Stardock is okay with this kind of thread for Alpha testers to blab little details to non-Elite founders, maybe other Alpha founders can chime in with little things they find.
Tech research -- while we don't have a detailed tech tree (its mostly just a tech selector for what techs are implemented), thus far they seem to have done away with those long iteration tech strings from the tree in GC2 (like Laser I, Laser II, Laser III, etc.). Instead, at this point, several techs which enable a planetary improvement or ship component (which we can't design our own ships yet, sadly) have three enhancements that can be applied (most have one to improve the effect of the improvement/module such as more firepower from a weapon or more production from a factory), a second to reduce the cost (so the same amount of existing production would take fewer turns to build a new factory, or reduce the time it takes to build a ship, etc.), and the third varies from what kind of item ... for a weapon, for instance, the third option is miniaturization of the component versus reducing the maintenance cost for a factory, etc. It does not appear these enhancements carry over to the next 'generation' of the improvement/component, but it seems that you need to research one particular enhancement for the improvement/component before you can research the next generation, which probably the biggest net difference between this tech.enhancement model varies from the GC2 model (where you had to go through all the iterations of one tech before researching the next version). Also, the enhancements only take a few turns in comparison to researching the next generation of the tech. If this model is retained to GC3 release, I think it provides good options -- during peacetime, go ahead and take the whole enchilada of the next generation of a tech, but during wartime when you are crunched for time and need to develop a quick edge, you can enhance your current generation of tech which can give you an edge without needing to spend a lot of turns researching the next generation.
Planetary development -- Brad gave us Elite founders some notes in the file repository he gave us access to (in addition to game music and art) prior to the alpha release in which he mentioned, as one of his notes, his own observation that the UI could use enhancement here, and he's right, so I won't bother mentioning its shortcomings. I think perhaps the biggest change implemented thus far is that instead of improvements just creating production (whether industrial production, research, culture, etc.) or a % increase to the planet as a whole, tile improvements can give a bonus to neighboring tiles (so building 2 factories in neighboring tiles, each of the two will enhance each other), so placement of improvements matters -- one factory neighboring six in adjacent hex tiles will be a lot more productive than building those seven factories in remote tiles; similar for research laboratories, market/trade centers, etc. Natural tile bonuses are still in, but unfortunately buggy -- but a big gist is there's more diversity of tile bonuses in that they can provide multiple enhancements both to that very tile and to adjacent tiles; one tile bonus, for example, can enhance production, research and influence for improvements built in that tile and enhance culture in a neighboring tile (I'm not quite sure yet what culture vs. influence is).
