Rob, I agree on the aerobic vs. anaerobic thought. Most of us who don't live/play at elevation probably benefit from emulating the expected workload in the Sierra or Rockies as accurately as possible - i.e., steady hiking with the occasional short burst of anaerobic effort in, say, a scramble. Deep, rhythmic breathing is one of the big keys in warding off AMS, and that's what I try to do in my workouts. Being accustomed to working anaerobically at lower elevations can be a bad habit above 10K' if you're not there often. Oxygen deprivation invites AMS.
I truly believe the key for me is sleeping 1-2 nights at elevation, at least if I'm going above 12K'. I don't feel any real ill effects up to 11K' or so if I've come straight from the lowlands, other than that weak feeling I mentioned. Lots of high-altitude research has been done on this, and the general medical consensus is that the body best acclimates by sleeping as high as is reasonably comfortable, and then going higher during the day. At least for expedition-style climbs. My one AMS incident seemed to be the result of staying in Lone Pine prior to a 2009 Whitney dayhike rather than sleeping high. I did several hikes prior to Whitney that trip up to 12K' without problems, returning to LP at night, but 13K' on Whitney-day did me in. Lesson learned.
