Never mind the fast switching, just having a whole slew of users is an unmitigated disaster. Ever tried to clean the spyware/viruses out of a system with 7 different users? I am seriously considering revising our standard price list for cleaning crap off systems so that it applies on a per-user basis. If you want to bring in a machine to have the spyware cleaned off and you have seven different users with the damn stuff, that's fine: we will bill you seven times the normal charge. Well, maybe an additional 33% per extra user, so that's 3 times the usual charge. It's at least three times as much work, after all.
Now to multiprocessing. I am astonished that anybody would even think about regarding a hyperthreading CPU as having anything whatever to do with being a dual processor. Hyperthreading is nothing but a poor man's remedy for a crippled CPU design that's incapable of chewing gum and scratching its arse at the same time.
Intellectually, we know better, of course, but we are still constantly getting surprised at the way that P4 systems bog down hopelessly at the slightest hint of a second task on the desktop. Start a Mozilla install off the CD-ROM, for example, and then while you wait, start doing some trivial desktop tidying - switch off some eye candy for example. Instant clag. A bloody Duron copes better than that, or a half-decent P-III for that matter.
Errr .... can I go now?