I'm a little late on this thread, but thought I'd throw in one more comment. I used to live in SEA, but live in ORD now, so no more AS for me. (Yes, I know I could fly to ANC

). I'm a UA Premier and really enjoy United, but to upgrade a non-full fare costs 15,000 miles, whereas AS only charges 5,000 regardless of the fare. So after one roundtrip to BOS, you are just shy of a one-way upgrade confirmable at time of booking!!
If upgrading is even remotely important to you, this is a no-brainer, IMHO.
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"I just wanna wish you good luck, we're all counting on you"
-Dr. Rumack