I personally ride Quarq and SRM and have had great results with both. Each has its benefits and challenges, but from a getting up and going standpoint, I've always liked the replaceable battery on my Quarq.
Just a note that while I've heard awesome things about the Garmin Vectors, make sure they'll fit whatever crank you'd consider them for before committing. Their receiver doesn't fit on all cranks right now but they're working on a longer wiring harness.
Specialized Bicycle Components