Dito, its indeed good news. Im having second thoughts though, as my Unibody MacBook has become slower with each upgrade, notably Lion. Restarting usually takes ages and beach balls are not seldom. If Apple is indeed cutting the cords for several Macs, this might suggest that Mountain Lion could require a sacrifice of overall performance.
Sounds like you need a fresh install of OS X. By that I mean truly fresh. Wipe the HDD and install Lion fresh. No upgrades. Then copy your files and such back over, but don't do a "back up" or "restore from a previous Mac" or whatever. Just do a completely fresh install.
I have the late 2008 unibody MacBook 2GHz. Upgraded to 4GB of RAM and a 320GB 7200RPM HDD. It's faster now with Lion than it has ever been. I always do fresh installs though. Never upgrade.