I have a P2K as my "only" bike (not technically the only one I own, but pretty much the only one I ever ride.)

If you're solo "most" of the time, you'll be perfectly fine on it. Reports of them being twitchy, difficult to climb, difficult to descend, etc are totally overrated. In fact, IMHO a "true" tri bike is more stable, comfortable, and easy to use than a road bike with aero bars. Of course, something like the Soloist is good at both, but still a compromise - for one thing, where do you put the shifters? if you use typical brifters, you have to take your hands off the aero bars every time you want to shift, so you're missing out on a lot of the advantage anyways.

And another note - when I switched from my last main bike to the P2k, my hill climbing times improved. Blame it on the placebo effect if you want, but I was quicker up hills than on my previous Trek road bike. (quicker down hills and on the flats, too!)