OK—I completely uninstalled LR 2.1 on the MacBook Pro and re-installed it. I removed every possible file, including the registration files. Even opening a blank, new catalog and switching between the grid and develop for the first time still takes 6 seconds...WITH NO PHOTOS IN THE CATALOG. After the first time of loading each module, it seems to switch much faster between modules.
I opened LR 2.1 in my office on the 24" Intel iMac. I noticed something that I'll bet is a bad omen. Upon launch the "Silvertone" splash screen comes up. I don't think I noticed this before, but it distinctly said Silvertone in a sort of Fender guitar font, NOT Lightroom. I ran the 2.0 beta on this machine some time ago, but can't think of why it would still be there and being accessed. I will do the full-on uninstall tomorrow and report back. Could it be so hard for Adobe to write in an uninstall script in their installer?
***LATER*** You can toggle the LR and Silvertone splash screens by pressing R. Don't know why, but the LR team are being cute.