Oregon has no sales tax, and as such its income and property taxes are much higher than many states. This is especially true in Multnomah County (where Portland is located), due to county income and business taxes on top of state. See, i.e.
http://credc.sterling.net/business/infocenter/Clark-Multnoma...
I've lived in both San Francisco and Portland, and anecdotally I found Portland's infrastructure and services to be far inferior to those in San Francisco: worse roads (climate doesn't help), more homeless, more difficult city bureaucracy, etc. This is of course somewhat subjective, so YMMV.
Personally, if I were to move from the Bay Area due to cost of living and taxes, I'd be looking at Texas.