They're fine. I've been using them for months as have several people I know. Let me just get you a couple of other discussion links that might make you feel more comfortable about the offer.
http://www.dslreports.com/forum/remark,8134724~mode=flat
https://www.wincustomize.com/msgboard.asp?BID=WC&id=217980#218076
If I had to complain about the service

, well...the control panel is dog slow sometimes, and the username/password scheme is a little odd and difficult to memorize. (You don't choose a username/pass as usual, you get a long string of numbers for both. For free I can live with it though.
Their prices may be a bit much but this free offer is for 3 years. Not too worried about that myself.