Product review (5 stars): works perfect
This works perfectly and is so much cheaper.  We've had it in for about a month and have not had any leaking that others have mentioned.  It does have an o-ring and instructions to make sure the o-ring is in place to ensure a good seal.

UPDATE:
1/11/2013 - We've been using these filters for over a year now and have never had any leaking.  I can't imagine evr going back to the brand name version.