Ways not to lock your bike

I just got myself a silver pair of these to replace my quick release
http://cgi.ebay.co.uk/BLACK-ANTI-THEFT-SECURITY-WHEEL-SEAT-SKEWERS-SET-OF-3_W0QQitemZ120498623121QQcmdZViewItemQQptZUK_sportsleisure_cycling_bikeparts_SR?hash=item1c0e471291

hopefully with a magnetic ball bearing in place they should offer security while being sufficiently easy to remove myself.
Better than carrying an addition cable lock

Well I normally D lock the front wheel to the frame and then the back triangle/wheel to whatever I'm attaching to so I don't really think I need these. Also if someone wanted to take your wheels wouldn't they just use an allen key on them?