I like it. it is a good motivator for me ,several people from my local bike club are also members so I try to keep up with or ahead of them in mileage. There is also a thread in the forum for a Century-a-month challenge that I participate in.
IMO only two minor negatives, One is that it has become popular and their web server can be very slow at times. The other negative is that you can't allow other people to view your journal. Both of these are so minor to me that it doesnt matter/