As I've said in other threads, I mine at deepbit because it is realiable. Aside from the downtime due to DDOS, I have never had any issues with the pool. I tried BTCMine, I tried BTCGuild, and both gave me issue after issue with no sign of it getting resolved quickly.
Yes, these other pools weren't up to handle the flood that came when deepbit was DDOSed. BTCMine is certainly having problems. But BTCGuild is doing great now with a new server up and another about to come online.
Anyway, I mine because I want to earn Bitcoins for securing the network. Giving one guy control of half the hashing power just doesn't jive for me. Mining solo is very reliable by the way.