For the longest time I was against buying pp, but to be honest, it can take hours and hours of time to get lucky on a drop. Or risking suspension by afk'ing and autolooting. Getting a mil pp for the sake of 30 - 50 odd bucks and then never worrying about merc costs, or maxing a few tradeskills using /mac combine... So yeah, I buy whatever pp I need now. (though maxed ts's so I don't need as much)
Ymmv though, if you're not working full time and don't have much disposable income, farm EW or KD or SL for droppable ac augs. Good pp.