If you've enjoyed previous TW games, I don't see any compelling reason not to get TWR2. It may not be the best in the series, but it's still a TW game. If you're like me and have a particular interest in the Roman period, well then it will be an enjoyable game despite its shortcomings. As Myth says, the game will be (probably? hopefully?) be improved as time goes on. Some folks are calling it "unplayable" right now...I don't really know why, I've played 200 turns. Yes it has flaws. The AI does stupid and annoying things, sometimes maddeningly so. Just like in previous TW titles. AI turns take a long time, which gets longer as your empire grows and you can see more of their units. Just like in previous TW titles. If such issues weren't enough to overcome your basic enjoyment of a TW game before, I don't really think they will be so with Rome 2.

As an aside, I do think it's interesting that you preferred Empire and Napoleon over Shogun 2. This is contrary to many others' opinions which I've read (I myself don't have one, as I haven't played S2). What I (possibly erroneously) infer from this is that your interest in and knowledge of the subject historical era is a large component of your enjoyment of the game(s). So...if Roman history floats your boat, then I think TW:R2 will probably do the same.

Can't really comment intelligently on your computer specs, I'm an idiot on all that stuff. I dunno, might have to set graphics to "medium" or something.