Of course, these days if you're serious about acquiring dropping domains you have to pursue ALL available means i.e. Snapnames, NW, Pool, DropCatcher, DropWizard, GoDaddy and more. Even then your chances are microscopic if it's a valuable domain since most of the main players have private systems and connections.
In my expiriance the better (more expencive) the domain name - the better namewinner gets.
Also - Enom - has the same kind of service but it's a $99 fee a month just to get in there and start bidding. The problem with Enom is that you will always get bid above in the last split second of the auction - I HATE THAT :-)