Ok. Let's get the bad out of the way first. That is, before the really good stuff.
Cons:
-The graphics are terribly basic, and run at a max res of 800x600 (ouch, yuck).
-The sound matches the graphics. 'Nuff said.
-It's incredibly complex!!! Avoid this is you are a casual 4x gamer. However, if you're a moderate to hard-core 4x fan you will probably love it.
Pros:
-It's incredibly complex!!! This means that planetary development, diplomacy (plus espionage), and econmonics are very, very detailed. This game gives you complete god-like control over a civilization. In fact more detail and control than any other 4x or Civ game ever published. There are govenors ("viceroys") who will help you manage many of these complex tasks. Contrary to some reviews (e.g. Games Domain) you can turn the viceroys on and off.
-It's addicitive. Like it or hate it, you'll find it has wasted half your day before you know it - even if you haven't enjoyed the experience.
-The exploration is top notch. There are artifacts and discoveries throughout the game that make pioneering a lot of fun.
-The ship creation system is back, detailed, and better than ever.
Hmmm:
-Combat is realtime. I can't decide whether I like it or not. However, you can always quick resolve battles.
Bottom Line:
Great game for me. It's a thinkers game. It's a strategist's game. It's an economics professor's game. All that makes the game a bit of a tough call for some. It may be too complex for many to call recreation. However, for the rest of us we can kick back and enjoy the ride.