This expansion provides very much needed end-game content. I loved being able to destroy worlds and build capital ships. Being able to include large ion cannons on starbases was loads of fun. It was also great to have special "edicts" I could spend unity on, once everything else has been unlocked.
The mauraders are a mid-game crisis. They are impossible to deal with, if you are one of the non-diplomatic agressive races. They are incredibly overpowered, and weren't too much fun to play with. I usually turn them off. You can also play an under-powered maurader, with the "Barbaric Despoiler", which allows you to steal pops from other planets. Fun in theme, but not very useful. Same with choosing a Post-Apocalyptic race. Fun theme, not really practical.
There are also a few new Ascension perks. One lets you kidnap enemy pops (great theme, you'll never use it), one that gives you increased sensor range and prevents other civs from reverse engineering your tech (multiplayer, maybe?), and the third allows you to build your "Death Star".
Parts of it I love, and add great dynamics to a great game. The rest, I'll turn off.