This expansion pack is fun, period. The new demons and weapons are great, and not so significant such that the old ones are forgotten. It adds more to the original Doom 3 the good stuffs that many said were missing and it makes the Doom 3 experience more satisfying.
First let's start with the graphics. Since nothing new is added to the engine, let's look at the texture and the look-and-feel. The levels look much more enjoyable because of the caves and ancient ruins look, compare to the high-tech metal look of the original. When I played the original, I felt cheated from the old Doom and Doom 2, where I really liked the gothic looks. Only the Hell level brings back memory. This expansion pack brings more like Hell, which makes Doom 3 really the Doom that it was meant to be. Monsters are good looking, 'nuff said. The engine to me simply is the best out there. So I grade this 10/10.
The sounds I also enjoy, but I like the melody type music, not ambient music. Doom 3 makes ambient music part of its scary atmosphere, but for some reason I didn't enjoy it. I wish music like Doom 2 were in Doom 3. The expansion pack continues the ambient music and good sound, which may be good to some, but to me is only okay. So 8/10.
Well, many complain that Doom 3 gameplay weren't fun. Somehow I must disagree. Games like Farcry and Half-life 2 have their own ways of fun. Games like Painkiller and Doom 3 have theirs. I liked all four games (which I considered the best of 2004) for different reasons. The expansion pack makes Doom 3 better, I think, because the action is more intense and wild. Half-life 2 and Far Cry have their action and adventure and mission-like gameplay, Doom 3 is simply "getting out alive" type of action. The expansion pack starts out underground and try to find its way back to the top, which essentially went through Hell again. The monsters, I think, are more well-placed and are harder to beat. Weapons are also more widely available, making emptying bullets into demons more enjoyable. The only thing I don't like about the gameplay in this expansion pack is the shortness of the levels. Obviously all expansion packs are often short, so oh well.
I think the new grabber gun is fun, but not as fun as Half-life 2 just because in Half-life 2, you can grab many more things. It's kinda funny in Doom 3 RoE, you can grab a big barrel but cannot grab a standing lamp :-) But then the grabber gun can grab dead bodies and fire balls and through them around, which makes up a lot. Finally, the storyline is good, not that original, possibly because Doom and Doom 2 have so many add-ons that all the possible Doom stories have been known already. I really enjoy playing the expansion pack though, more than any other ex-packs (MoH, CoD...), so I give this 9/10.
Well, overall, I got this game for $30 at Target, which is $5 less than retail, and it was much more fun than those $30 ex-pack of other games, so I think my money was worth it. Some people enjoy Doom 3 and think it really lives up to its expectation, some do not. I'm one of those who thinks Doom 3 is the best, though I must admit 2004 brought forth some of the funnest FPS games ever, seriously. So far 2005 has BIA and now D3:RoE, hopefully more will come, and can't wait for Quake 4.