Oleg-
Big replay value and many different ways to win. The tech tree is never quite the same every game, they made it slightly random every game. So far playing several different games I have actually missed certain techs, and gained new ones. I personally like to blow everyone away as the Ithkul (which is tough, even though they are a "super" race...everyone hates them), but am in the process of trying other ways to win (senate win/discovering the X's). Insane tech tree. So far what I do is colonize like mad and go heavy research (like I do in SE IV). I try to grab a huge area early on and hold choke points, then colonize by "backfilling". I HIGHLY recommend building spies early on (as many as you can afford), for defense & to steal tech esp. research spies. It's hillarious to send 4 research spies against somebody and steal techs right & left, and to stunt their research by sabotage.
Atrocities is right, the star map is awesome. Some people say the graphics suck, but I disagree. The combat graphics are good in my opinion (could be better, but then again the game was largely designed several years ago), but not on par with say a CIV III. I DO recommend a good graphics card (I have a GeForce 3 Ti500, and the game rocks) and a fast processor/decent memory (I have a P4 1.8 GHz w/512MB DDR-333 RAM). That is one downside to the game is the somewhat high system requirements. The only other thing is it gets to be a headache to micromanage once you get 20+ planets (which at that point you should be using the AI to help out). I'm still a die-hard perfectionist and I have a hard time giving control over to the AI, but it does a decent job and I am slowly getting used to it.
Hey Atrocities, I play fair against the AI in SE IV (really I do,lol)

I just think it's a minor thing (diplomacy) that could be fixed in a later patch.