Live Chat help seems to fix just about every single problem we have on the fly, and they open Tickets when it gets more complicated, with thorough and fast follow-up.
I have never been happier with my hosting support, and I've used company after company over the years. I've now been with Rackspace (Sites and Cloud Servers specifically) the longest.
I should note that I ended up with them because they took over SliceHost (also great support), so I didn't really "choose" Rackspace based on anything, but loved SliceHost, and the transition was seamless, and the great support seemed to follow.