A lot of people don't like RackShack because they do not provide a managed server. When you get a server from RS your on your own. The only thing they will do if you have a problem is restore your server to its origonal state. If its a hardware problem, they will replace it.
A lot of the negative feedback from RS is from people that have gotten a server and have no idea what they are doing. They then take to the forums and complain about it, but they new exactly what they were getting into.
We have been with RackShack since Sept. of last year. Other than a few hardware issues we really don't have much to complain about. There have been some issues regarding some of there service that was not up to par, but they seem to be listening to feedback by fixing those issues. If you know what your doing, by all means go for rackshack, if not, get a managed solution elsewhere. Managed will cost you quite a bit of money, so be warned.