With LCC 1.6.6 the app switch button on my MX300 did not switch apps; it would only tab between active fields on the foreground page in the current app. Did this with two different MX300's on two different Macs with fresh OS installs. Bizarre, to say the least, but LCC 2.0.0 fixed it. Excellent!
--
MX300 mouse, OS X 10.4.6, iMac G5 1.8GHz 17"
Logitech Control Center
For their USB mice & keyboards.
Version: 3.1