It is an EXE only (copy to your device and run), which has a basic GUI which allows you to scan for duplicates, and then choose (after being told your duplicate count) whether to remove them. Contacts are compared based on 'File As', field, 'Email' field and 'Home / Work / Mobile' phone fields. If all those fields match, it's deemed a duplicate.
The application scans my ~200 contacts in under 2 seconds
Hope this is useful!
Enjoy, feedback welcomed! If you use the CAB, please consider donating £1 to my 'quidapps' effort to develop cheap, useful applications and tweaks - click here to donate. Donations will be used specifically to buy development tools to enable slicker and more advanced tweaks and applications in the future while retaining a £1 price point!
PS If you think it's worthy of me cabbing up, or extending to Calendar support etc., let me know!
[Edit: Now available by request in CAB form with AppToDate support without registration required for download: http://www.apptodate.../dupededupe.cab]