I mine for deepbit, and I'll tell you exactly why I do.

After deepbit was DDOS'd, I decided to try some other pools.

I tried BTCMine, and had issues.  7% stale shares, consistently.

I tried BTCGuild, and had issues.  Loads of idle miner times that cost me hours of mining.  Definitely more than a few percent, I would guess around 10%, but could have been way more.

I went back to deepbit.  Everything was fine, my generation was consistent, always under 1% stale shares (which are paid for anyway), it's extremely reliable now that Tycho has gone through a full DDOS attack and knows how to fight against it properly.

It is well worth it to mine at deepbit for the reliability and attentiveness of Tycho to any problems that arise.  It is worth paying an extra 0.5% to 1.5% effective fee rate in order to have 100% uptime, instead of 95%.  It just makes sense.