Ok, played a bit more today (PC version.)
Totally digging this game. I love that Volition took it one step further from SR3, and kept what was good about and then added even more awesome stuff! The graphics are still superb (maxed out), runs smoother as butter, very polished.
The intro mission is amusing and CoD-esque, and then goes the deep-end into zany sci-fi land, sort of like Independence Day but even sillier.
I think anyone thinking this is just an 'expansion pack' has nothing to fear. I'll sit down with it for a few more hours tonight and add some more impressions.
Also, Nolan North being his own voice and self-referential fucking rocks. I'm playing on a GTX 760 with Nvidia 326.58 drivers BTW. Once i grab another 760 for SLI tomorrow, I'll crank this sucker up to 3200x1800 downsampled, should still run like butter. If you've got a Radeon 7850/GTX 660ti or above, you can crank this up to max settings @ 1080p and not even worry about anything less than rock solid 60 FPS.