I have just download Version 4 (beta) and it looks good and is a tad faster on the scan, most of the changes are under the hood. A nice addition is the facility to repair the control panel - I like it

Scanning engine improvements to detect rootkits that keep handles open to themselves Ability to remove most infections in a single pass/reboot Improved trace detection Windows Vista Scanning Improvements Additional repairs for Windows Vista and Windows XP (System Restore and System File Checker (SFC)