It just feels like a lot of thought was put into the game's design. The way you slow down when you get hit by a bullet. Not being able to jump and shoot at the same time. Support has a lot of ammo while machine gunners don't. Machine gun, sniper and rocket are damn near useless before they can run to a spot where they can camp. You need to deploy machine guns and rocket launchers before you can fire them and they are heavy and cumbersome to carry. When you're playing assault, there'll be moments in almost every round when you wish you were a rifleman instead and vice versa. When there's a machine gun up a head, you're scared of getting butchered. But when you're actually playing the role of machine gunner, you're constantly worrying about smoke grenades, having to reload in a bad time, rifle grenades etc or having to get up, sprint and move when your team advances and it makes more sense to move the MG further up ahead.
Support weapons have crazy recoil (not to even mention trying to shoot a machine gun with out mounting it first: your cursor will be pointing at the sky in less than a second). The American rifle M1 has more rapid fire as it's semiauto and 3 more bullets but it requires 2 bullets to kill an enemy and you can't reload it, while the German rifle (K98) is a lot slower as it's bolt action, has only 5 bullets but kills from one. Well shot rifle grenades are really important in taking out MGs&snipers, forcing MGs to retreat and creating temporary no go zones for the enemy.
I guess the only criticisms you could make about the class system are the fact that there's no medics (or even engineers like in Enemy Territory), rocket launchers are kind of useless (I'm sure in the right hands, in other words clan battles, they're utilized well) and K98 is more useful than M1 often times. If there's a MG/sniper up ahead and you know where it's located, as K98 you can easily strafe from your safety zone&shoot quickly and that way kill the MG/sniper/RPG before they have time to react, while with M1 you wont have the time to do so.
The level/map design is as stellar as in Counter Strike, which is a crucial part in giving the game a sense of depth&tactics.
Another noteworthy quality is that this game is not only a great team based tactical FPS, but it's good for newcomers. And it really is a team based game. Even when playing on public servers and not communicating to others, I really have the sense of working towards a common goal with my team mates. Very few other FPS games manage to capture that feel outside of clan battles. You'll often make sacrifices to help your team: delay the enemy long enough so your machine gun can run into position and deploy his gun, stand in front of enemy fire so that your team mate can arm/disarm a bomb before he gets annihilated, getting killed by enemy MG fire so you can distract it long enough that your team mate can run and capture a flag etc. The game is full of those small term goals and achievements. Even if you die, it feels like you've accomplished something and helped your team.
Since you spawn often and you can be useful to your team even if you're not a super accurate pro gamer killing machine, the game is more easily approachable than other competitive shooters that are well designed like Counter Strike and Quake, where you're either a burden to your team (CS) or get instagibbed constantly.
I'd also like to note that the game is audiovisually excellent. The Central European architecture is beautiful and back in 05/06 the game looked great, still does in fact. It doesn't just have good graphics, the game is stylish (like the 30s/40s style posters in numerous levels). And the audio design is superb. The loud cling of the Garand clip is music to my ears and especially the machine guns and explosions sound really menacing if you have a decent soundsystem/subwoofer. You can really "feel" those grenade explosions and they make you retreat easily (psychological effect, which you must use to your advantage when defending/assaulting objects). Not to mention the terrifying sound of the German MG in the distance, even the wikipedia article on MG42 states
So distinct and terrifying was the weapon that the United States Army created training films to aid its soldiers in dealing with the psychological trauma of facing the weapon in battle
Oh and this game has an epic intro theme.
http://www.youtube.com/watch?v=9MKDq2sXMH8
http://www.youtube.com/watch?v=84xJm5Q5__8
One more feature of this game that I'd like to mention but can't quite put into words eloquently: it's like Counter Strike also in the way it's fairly realistic in many aspects, but also arcadey enough to keep the game fast paced and fun. Something like Red Orchestra, as good as it is, isn't great for short gameplay sessions.
This game turned me into a WW2 fanatic for a year of my life so I obviously have a lot of nostalgia towards it, but I think that it's still a damn fine and well crafted FPS, something that you don't see often these days (thoughtfully crafted online mode that people will keep on playing for almost a decade). What does the Racketboy community think of this game? I think it's underrated. If you have a Steam account and haven't played this game, do it now.
