It is not among the most popular quilting setups. I always think that there are reasons for that, so I stick to well-known and popular brands -- especially since machine quilting setups are costly, bulky, and hard to resell if you decide to change or upgrade later. If this is your first foray into machine quilting, I would look at something used or else check out the better-known brands such as HandiQuilter, Innova, etc.
All of the posts I have seen about the Block Rockit have been very positive. Have not seen complaints about tension, etc. but that doesn't mean they're not there, just that I haven't seen them.
The homequiltingsystems group on groups.yahoo.com is a good place to solicit opinions about various machine quilting setups within your price range. I think that is where I have seen quite a few posts about the Block Rockit.