Countdown was ok for a dollar, but some of the dialog was out-of-character and I really haven't liked Winick's decisions lately.
Powerpack is out of continuity, so it has no relations to the original or current Powerpack.
Runaways on the other hand is awesome, and I believe Vaughan has a deep respect for Runaways. But that doesn't mean you can't joke around once or twice. "Power Vacuum" anyone?
GLA looks great and I'll definently pick it up, once it's collected. Since it's Marvel, it most likely will be.
Ultimate Secret is written by Warren Ellis. Therefore I'll probably buy it. You have to remember though, Ellis usually writes decompressed, so it will probably read better as a whole.