If you love Sins, you'll love Rebellion.

O.K so the new additions are well worth the asking price. The game has changed drastically but if you already own diplomacy and feel it is superb i would wait a little while until picking up rebellion. For me it was well worth it because the added units, factions and tech trees has altered the game immensely

Haha, I bet the new release syndrome has showed itself in the forums although I had not noticed it. Example, right after a game is released you get lots of complainers and trolls in the forums no matter how good a game is. I did notice some solid reviews coming in so it is on my to buy list. I still have endless space and legends of pegasus on that list as well. Too many games, too little time.

Sins Rebellion is still a fantastic single player and co-op vs AI game, and the new content only makes it better.  Competitive multiplayer...has issues right now.  Wait until the next patch if that's your main interest, or at least for the trolls to stomp off and go somewhere else.