Just host is a great service that we are currently running Tweezermania.com on; it has many great features and we actually took advantage of all their offers and it was like we payed nothing for 2 years. We got their google credit and used it. and did the same with the yahoo and bing credit. We actually generated a couple of sales from the credit so it was like we got payed to sign up for this service.
Since we have had this service now for almost 2 years we have had very little problem. Once there was some downtime form a security issue they had on another user but it has since been remedied and my site was only down for about 2 hours and they stayed in contact with us the whole way.
There is a lag if I have about 20 users on there at once witch is forcing us to upgrade to a vps. I’m sure there would be no problem if I wasn’t using a resource intensive script like CS-CART. If you were running wordpress I’m sure that you could have 50 people on there at once before you noticed a big difference.