I've been having this problem for a few months (using stock 2.1 and now stock 2.2). Upon returning to the home screen, intermittently the wallpaper (regular) will display but it takes 3 to 10 seconds for the icons to display and the device to unfreeze. Its very annoying. I uninstalled LauncherPro and started disabling widgets one by one until all widgets (including google search bar) have been removed. I then started turning off weather alerts and other background updates. No luck.
I installed SystemPanel (paid) and ran monitoring but nothing out of the ordinary stuck out. No one process is constantly sucking up CPU, but something is probably blocking while I load the homescreen (again, its unpredictable and works lightening fast sometimes, and painfully slow at other times (usually when I need to do something quickly...)).