Allthough the main quest was rather, uh, short, I liked the game very much on my first playtrough. But as someone pointed out beforehand, I more or less roleplayed it through, giving the clock some more time to run. I finnished at around 19 hours played, which is a damn shame since I feel like I missed most of the good stuff, and I know I did.
But yes, the missions after G.E.C.K felt like "let's finnish this alredy". I would've definately liked to see some more to the main questline.
Exploding heads are awesome, though. Very awesome.
The very ending with the purifier I thought was absolutley fantasticly thought out though, but then again this is like my second RPG, so not many referancepoints, really. Without trying to spoil it too much, I wished my character would've been playable AFTER the purifier got turned on. Perhaps some kind of mega rad-away would've justified it.