So, 6 months ago I made the switch to Site5. Smooth transition, great support. The first two months were perfect, only one downtime due to hardware failure (a router on the datacenter failed, as I recall). The forum is very active and useful and is getting better every day. The first bump came with Superhosting, for a week or so, support was way slower than usual (usually it takes 15 minutes to get an human response from support). Support got back on track and is doing fine right now. Server uptime was always in the 99.9's during these 6 months and I can't complain about that. Lately, server load is sometimes higher than I would like it to be. Backups and probably more people using the server makes the load goes up. Most of times it is under 4.00 (it's a dual xeon w/ 2Gb RAM) but twice in last 2 months went as high as 13.74, in both occasions failing Eximstats. The first time support rebooted the server and the load went back to normal. My Site5 (custom panel) is very useful and is getting better every version. I can easily see my billing information, ticket status and other things. Recently support added a new IP for one of my domains for a very reasonable price ($1/mo) and instaled for free a SSL Cert I have bought (the SSL intall fee is waived for resellers). Of course, Site5 is not perfect but it's the best host I know and I am very satisfied with them.
6 months is a decent amount of time to judge a host and your review is well balanced. Over enthusiasm can sometimes partially kill the credibility of a review. Thank you for taking the time to update us on your experience with them.
After being referred by a trusted Movable Type programmer, I switched over. So far I've been really impressed with their prices, service and support. I'm switching over from a host using hSphere, so some of the terminology/approach has me a bit befuddled. All in all I've enjoyed them though.