Read the specific complaints of people on the forums here and elsewhere. Forget the glowing reviews and read the complaints. If the stuff people complain about sounds like it'd annoy you, then skip this or wait for a Steam sale or GOTY edition or whatever.
If the stuff people complain about doesn't sound that bad to you, then go for it. Plenty of people like the game, plenty of people can't stand it. Only you know your own tastes, but you can get a lot of information here about what people see as problematic.
Bottom line: you know that the positives will always sound positive. Great graphics! Cool new features! I love it! Etc. I've learned -- the hard way -- over the years that positive reviews mean squat. Many times, the stuff people say they love, it turns out I don't love the same way if at all. The stuff I love are things other people say they find annoying. Plus, people tend to give you only a very surface level "it's really cool and pretty!" answer on positives. That's because they're too busy enjoying things to bother explaining why. Perfectly understandable.
By contrast, people who are NOT happy with the results will often go into detail about why. That's because venting about this stuff is a form of catharsis. Again, perfectly understandable. But the upshot of all of this is that a negative response -- especially on a forum like this -- will often include a lot more raw information than a positive one. Maybe what people say they hate won't bother you in the slightest.
I know folks here have complained about, for example, river graphics. I don't recall anything bad about them, to be honest. I'm not a huge fan of the new road graphics, but...really...I don't care that much. Still, some folks will mention that in complaints. Some will say they dislike how static the tiles are and how the Civ 4 tiles were so much more animated and fun. While I agree, again, that's not something that, if I read it before buying, would turn me off to the game.
On the other hand, complaints about, for example, psychotic AI, weak AI tactical abilities, problems with 1UPT (one-unit-per-tile), map scales, build times, tech speeds, tile yields, etc., THOSE are things I'd pay attention to because I recognize that they'd be the things that'd most affect my enjoyment of the game.
Only you, however, know what you do and don't enjoy, and therefore only you can determine if the negatives about this game will bug you. In my opinion, it's worth doing the leg work up front to determine whether this game is worth your $50. I did not end up thinking it was worth that much, frankly, but that's my view. Read the negative reviews and draw your own conclusions. You know you're already positively disposed to the game, so the ultimate question is "What's everyone think is so bad about this, anyway, and will I care about it?"
