I like to rinse the yeast cake 3-4 times with boiled, cooled water. This lets me get the trub out (what falls out first) and the dead cells (what falls out last). Then, I calculate the pitching rate using the lowest setting for trub on the MrMalty app. If it is older than a week, I give it a little wake up juice starting the morning of brew day (to be pitched ~ 12 hours later).
I will save yeast from APA's, but generally not IPA's as I late hop them heavily and go high gravity. This really stresses the yeast and coats them significantly with hop oils. I believe the theories, as from my own experience it takes a lot more effort to clean yeast cakes from these types of beers, and I observe a lot more dead, floating cells during the washing process. If I dry hop in the primary fermenter, then I don't even consider saving the yeast cake. It's nearly impossible to get the yeast clean. If you transfer to secondary, then you can dry hop all you want without ruining your yeast cake. However, the trade-off is that you have to let fermentation complete and wait for the yeast to completely flocculate and settle otherwise you will begin selecting for early flocculators. This prevents you from throwing in the dry hops when fermentation is 2/3 complete, thereby letting the yeast soak up any oxygen that comes in with the hop pellets.
Usually, I use the american yeast strains on hoppy beers. Since these only cost $1-2 per dry packet, I don't worry about not saving the yeast. For all other beers I use specialty, liquid strains and put in the extra effort to keep the cakes going.