I can honestly say, after using slush for a couple of days while btcguild was down, that I feel sorry for the people who mine with slush full time.
Can you explain why?
Should be obvious - if you don't switch pools when one is DDoS'd then your rig is sitting idle not making money.
Slush - what's the word on service? Are you considering any kind of SiteBacker DNS load balancing to help with traffic distribution between colos - that's helped some of my environments with DDoS.