I have been using SeeksAdmin for a little over a month now. I chose them because I was having issues with my managed server company taking an extremely long time to resolve issues (some up to 7 days with no communication). The first issue I had with them was Frontpage Extensions not working. Tris and his team had this situation resolved in 17 hours as compared to 7 days and running (and Tris apologized for taking 17 hours to get this resolved, I was ecstatic getting this fixed in 17 hours as I was expecting longer!!). They normally reply to my tickets within 20 minutes or less and situations are usually resolved in an hour or two (for normal status tickets). I have had one high status ticket which they responded to within minutes and the situation was resolved in approximately an hour. John is the staff member who is usually assigned to my tickets and he does an absolutely fabulous job!
I have used a couple management companies and these guys are definitely the best!