Wow Loren, I'd be bummed to see you move, but I can understand the draw that SLC has for you. I'd selfishly tell you to stay in SF, but I honestly think that this opportunity for you to do what you love as more than a hobby (well - that's good & bad, of course...) WHILE still working for your REAL income sounds too good to pass up. Sounds like your friends' business needs someone to focus on expanding and running their business - since you'll be Kelly-less for a year, you can really focus on that.
I hear what you are saying about coming back to SF with the rent situation, but dude - if SLC doesn't work out, or you change your mind for whatever reason, you can ALWAYS figure out how to get back into SF. People with much less intelligence & resources do it daily!
I think I'd go for it. I also ABSOLUTELY LOVE San Francisco, and can't presently imagine living elsewhere, but if the opportunity to pursue a dream opportunity in a semi-cool place came up, I'd also be more than tempted.
Hope that's food for thought...
- Jon