When using WinCache users cannot delete files / folders until the application pool is recycled. This is quite a big deal as it gets anoyying constantly having to reset the application pool so for instance vBulletin can continue to run (must delete the install folder), WHMCS (must delete install folder) and other scripts like this.
When trying to delete a file / folder you receive a notification stating the file is in use. This issue goes away once WinCache has been disabled or the application pool is recycled.