Sean,
Tom is right regarding the tees at Chambers Bay. Playing at 6600 or 6700 yards is really the best way to feel the real flow of the course. Holes such as 5, 9, and 14 all require big treks to get up to the tee boxes. I think the course is made better by these tees, as Washington undoubtebly needs a course that can sustain a major or big event, but as far as flow is concerned, a couple tee boxes do require big treks.
As far as mix n' match go, I have no problem playing varying sets of tees. From the back tee markers (not the tippy tips) at Chambers I can reach two of the par-5's, sometimes more or less depending on the wind. However, I played #14 at 498 yards and didn't stand a chance at reaching the green into a 30 mph wind, despite its downhill nature. On a hole like that I wouldn't mind moving up. For the matter, I play the lower and back tee box on 17 because for me, its a better hole from there. Playing from up top, I hit 8-iron past the pin from 172, and so the hole isn't really hard at the back tee markers. At 217 and a bit uphill though, its a real great hole.
So, I definitely go mix n' match sometimes.