Ugh, so I thought I'd reseat the heatsink and I really shouldn't have. After doing so my temps were higher (creeping up toward 50C at idle). Maybe I didn't clean the old thermal paste off well enough, but I'm pretty sure I also didn't apply the new stuff properly. I'd always read/seen that you don't want to use a lot, and I didn't, but maybe I didn't use enough, or maybe it didn't get spread out enough on the processor (I used the "small pea sized amt. in the center of the CPU" method). I think the next time I'm going to try to spread it around a bit.
Also will rubbing alcohol make a good enough solvent to get the old stuff off properly? That's what a link at PC Gamer recommends.
EDIT: In my research it turns out a paper coffee filter makes a good lint free cloth, so I grabbed one, cleaned off the old stuff really well, applied new stuff to the heatsink surface, and used one of those square plastic doohickies from a bread bag to spread it around nice and thin. Reseated, and...SUCCESS. Idle temps at around 30C.