The AI is weak and it has a few bugs, but it's a working strategic WW II simulation and that's good enough for me.
I think the game is fantastic. There are plenty who disagree, but I'm a WW II strategy gaming fanatic and can overlook the poor documentation, bugs and generally poor AI ("Der Fuhrer" can be particularly idiotic and suicidal at times, sometimes getting fixated on some minor campaign, sometimes declaring on Russia when the Wehrmacht is pinned elsewhere - which I suppose is almost somewhat realistic ... ) It's a blast to invade France, launch Operation Barbarossa, land at Normandy (or avoid it altogether by stopping the Nazis in 1940) and so on. You also have a pretty free rein to check out alternate scenarios (say, have your Germans invade Spain on a drive to Gibraltar, or have your Bolsheviks surge through Turkey, or a host of other ideas).
The gameplay is generally smooth, even though the control interface is somewhat awkward. One bad habit is for the game AI to take very long turns when there are lots of units in play - this is especially the case when the Russians and Germans are at it. But there are plenty of good points to compensate for the problems - a clever research system, build queues, an Atlantic War with submarines and escorts, nice chrome writeups on the leaders, and plenty of other extras.
This isn't as well done as Panzer Tactics, but is a grand strategy European campaign rather than an operational strategy game. What annoyed me about the latter is that one was always playing battles along a track - there were unlockable battles that added some variety, but the game really didn't give you the feel of an open ended environment. Europe at War does - you can really do just about anything you want within the game parameters. It reminds me of a handheld version of the old Strategic Command game.
If you want to play the European theatre of World War II on a Nintendo DS (and don't mind that you'll be doing it solo - there's no multiplayer option, not even for hotseat play), this is the game for you. It has numerous flaws that will annoy the average gamer, but if this genre appeals to you they can be easily overlooked. I've been playing for several days now, and have completed the campaign twice for the Allies and once for the Axis. I'm very pleased with it.