If you are willing to get yourself inmersed in a mature, realistic simulation ot WW2, there is a lot to enjoy here.
First thing: the graphics engine it uses is quite outdated, and that gives a bad impression to newcomers. Those who don't care so much about that, but about gameplay and depth, won't be dissapointed.
This is a "hardcore" game: the amount of keys, the very slow pace and the attention to detail - that encompasses a high level of realism - is big enough (in fact, there is no other game like this) to satisfy mature players with a love for good, serious games. And it feels a void left by Battlefield 1942 and that others, such as Battleground Europe, are not filling.
Pay attention, young gamers: This is no Day of Defeat or CounterStrike - that are faster and far more "to the point". It's also much slower than the Battlefield series, so although it may be catered to a similar public, it could be slightly difficult to pick up. Keys are somewhat akward in the beginning, but later they begin to make sense and are confortable - for a game with more than 20 actions you need to remember - It takes about a day or around 10-15 matches to actually begin to figure out what's going on. To be an expert... well it seems like you are going to need to spend an awful lot of time with it. So if you are into it, you'll really love it. It needs a lot of commitment.
The sound effects are good, as is the interface and hud. Nothing too complicated of flashy, just good old-school indicators. Some of the textures and models stand out, but others show signs of age - but the amount of work and skill shown by the programmers, and what they've done to the UT2004 engine is like a miracle. Unfortunately, although some maps are brilliant, deep and inmersive, other are not so enjoyable. The animations are somewhat stiff. UT2004 has to show its age somewhere, and that's the worst of this game: its engine is too old to be sold as a full-fledged (and full-priced) commercial product. It doesn't quite feel like a mod, indeed not at all, but it does feel like something we would like to see updated, and not like something you are going to be willing to inmerse yourself in over the next couple of years. It's like releasing a BF 1942-engined game when things like BF2 are around. Graphics are not the main point for mature gamers, but still, now that we have nice and shiny new graphics cards we might as well see them being used. On a mid-range system you can easily crank up everything to the max and still get really-playable frame rates, which is good, but not when your tank gets stuck on a wooden fence or a piece of tree. And talking about trees, some "forests" require a fair deal of imagination to actually see them as forests...
Overall, a 7 seems like a good score. The game, wan't it for its UT2004 backbone, should really receive an 8, even a high 8, but the price tag is too expensive for such an outdated engine. It's an amazing effort, a mature, realistic simulation, it's just a real shame that its engine shows its cracks, really a shame, as the amount of work put on this game (and on updating UT2004 to such a wonderful level of detail) is huge and it feels really special. It's a tiny jewel... beautiful but a bit old.
On the other hand, it plays flawlessly even in low and mid-range computers (not surprisingly).
To end this (long) opinion ;-) , I think most of the people who complain about this game have been put off by its graphics and complex gameplay, and it's realistic and no-nonsense approach. Some of these players haven't had really given the game the time it deserves to be experienced fully. It will not be enjoyable for many multiplayer FPS fans, specially for younger and more impatient ones: It's pace is extremely slow and you have to walk long distances if you don't choose your character class carefully and know what you are doing - what can lead to the impression of having to walk around doing nothing only to be blown to bits by a tank - as some comments here show.
For the mature gamer it's a jewel. A real one. It will satisfy hardcore gamers with its unbelievable detail and strategic depth. There are not many games like this, and it does need to be played along with tools such as TeamSpeak and a good, dedicated group of friends / clan members. The fact that tanks can only be useful with 3 crew members working together and communicating effectively shows the intended audience. This is not a lone-wolf FPS to spend a couple of hours with.
If the developers had put a lower price the game could be an instant hit, I am sure Red Orchestra 2 with a better engine will be a major success on the community.
But please, if you don't like it, don't say the game is bad... because it's not. It's brilliant and truly amazing, and over 25's will appreciate it in all its extent. Those kind of gamers are also not so concerned about how old the graphics engine is, so they might feel more inclined to forgive some of its glitches and the overal rigidness of UT2004.