I tried the Demo and I have mixed feelings.
As far as stability and performance goes it never crashed for me, no stutter either, and it runs smoothly on my system at Ultra settings with 4xMSAA and 16xAF, but I really don't like the shadows effects, especially that I could see some shadows through some smoke and even through flags and banners in turn creating what appeared to be artifacts at first glance, but then when I saw a shadow silhouette of a soldier through a flag, and all pixelated at that, then I realized that shadows may have issues in this game... or it's a driver thing (I'm using 182.06). But outside of the shadows being messy the rest of the graphics (textures and all the particle effects, especially water and smoke and even animations) are just superb, they're simply what one could expect for a modern DX9 (is it also DX10?) game.
The load times as mentioned however are indeed very slow, both for going to and from the main menu and also for loading maps in general, although I can understand the increase in loading time if the graphics are better than previous games since there's just more data to load and higher polygonal models as well (at least at High and Ultra settings). It's not a game-breaker for me at all, it's annoying but I can certainly ignore it, once the map is loaded you forget about it fast enough.
The actual game-play... somehow I think they missed something with ground battles, it feels slow-paced, but there's only one battle and tutorials, so it's not going to show everything that we might do in the Campaign or in multi-player. The naval battles on the other hand are good, it's a great addition to the Total War series, it was asked by the community since the days of the original Medieval: Total War and at least we have it, and thankfully they didn't screw it up, I'm glad to see a good execution of it. I like the fact that the ships don't move too fast as to simulate a more realistic approach to speed. For instance the naval battle of course provided in the Demo shows just that very well. At the beginning the ships are slowly but surely moving on a meeting-type column of classical side-by-side confrontations (which as a side note was used often in Star Wars during space battle sequences, especially in Revenge of the Sith at the beginning).
I simply like the "massive" and "imposing" effect of the slow ships firing those cannons at once and the missing projectiles falling in water (which just looks beautiful in my opinion). And seeing the ships crew working around just adds to the ambiance. I really like it. For me that's the best part of the Demo, but I don't know if it will be the best part of the final game, I don't think it will, but generally it's just a great addition and to repeat myself they executed it properly and it shows up in the Demo, it's fun, simply. I'd like to come back on the ground battles however. As I said it feels slow-paced but I'm not quite sure at what to point exactly being the cause of that feel. I think it's simply due to the context of the battles presented in the tutorial and the one ground mission we have, such a context simply asks for things to start slowly. I'm confident that the final version will deliver. I'm especially excited to see how sieges will play like (if there'll be any).
And, finally, something that irks me is the camera. I almost managed to get the TW-style camera (there's an option for that, I know, but it didn't do what it does in the previous TW games). Everything seems fine except when I want to "strafe" left or right, the thing is if I bring the cursor for instance to the left side of the screen then instead of strafing it will actually rotate left, and I tried all I could to make it strafe instead, but I didn't found out how, anyone got any suggestions? And finally, if I double left-click on any location on the map during battle it doesn't bring the camera there (not a zoom, but actually moving the camera there very fast like the previous games), again I didn't found out how to do it, and again I ask for help on that, if it's possible or not.
Overall I think that Empire: Total War will live up to its name and that it won't win the "worst of the bunch" prize. Nope, instead it wins the "best polished for a vanilla version" prize in my book. It looks good, it plays good enough, the addition of naval battles will be great, the formula is all there for yet another successful Total War entry in the franchise, good job Creative Assembly and SEGA, I'm confident that it will succeed. I for one will buy it at its full price and won't wait for any specials.