If you want to check the performance improvements of Flash Player 8 compared to FP7 then make sure to install the Flash Player Public Beta:

• http://www.macromedia.com/software/flashplayer/public_beta/

After the very smooth installation experience Flash Player reported a version number of 8,0,0,434

The Player team did a great job to get things right: FP8 uses far less memory and comes with a better garbage collection. Also, the overall playback experience has improved - in general, almost every content you've ever created will perform better on FP8. We tested one of our bigger Flex applications with FP8 and it consumes about 30% less memory and significantly performs better in terms of screen redrawing and initialization times when using deferred instantiation.

BTW, a great tool to easily install and uninstall several versions of Flash Player is the kewbee Flash Plugin Switcher

Dirk.

http://www.yaodownload.com/audio-mp3/playertools/super-flash-player-manager_playertools.htm

http://www.purchaseshareware.com/multimedia-design-video/quick-flash-player8890-3.htm