The last three times I've gone to the U-District Starbucks (the old one - they're bluilding a new one), I've have two excellent drinks and one mediocre one. This is better than the running records of many coffee shops on the Ave, sadly, but there are at least two with better records than this (which I will probably review separately elsewhere).
On the other hand, the Starbucks on Broadway (near the QFC) consistently gives me excellent drinks - I've yet to receive a sub-par drink from there.
I've occasionally stopped in at other Starbucks, and most of them seem to be very hit-and-miss - often more miss than hit.
Add to that frequent long lines and often insufficient seating in some of the busier locations, and Starbucks isn't that great. Their prices also seem to be slightly higher than the hole-in-the-wall coffee shops.
However, I would say that they are slightly better than a random coffee shop - drinks are often mediocre, but *very* rarely undrinkable, so if I'm in an unfamiliar area I'll go to a Starbucks rather than a random hole-in-the-wall.