I originally had my site hosted with HostGator.com. Unfortunately my site outgrew their shared server package and their dedicated servers were too expensive. I then started to search for a new host. For the next four months my site would be plagued by severe downtime, unresponsive hosts, terrible customer service and enough frustration that had me seriously considering shutting down my site for good. My last gasp effort was URLJet.
When I switched my site to their server (my fourth server move in as many months) my site was plagued with SQL errors thanks to incompetent hosting companies tinkering with my site before them. URLJet was able to diagnose all the issues and get us back online in no time. They have also had the best customer service of all the hosting companies I have ever been with. They specialize in hosting vbulletin forums and they are adept at dealing with the issues vbulletin sites have. When I send in a support ticket I never have to worry about waiting too long to get any support. They are always courteous, professional and able to diagnose and fix any issues I have had. My site's uptime has been 100% since I have been with them and I plan on staying with them for a long time.
If you are looking for a hosting company and are not a vbulletin "guru" then I recommend URLJet.com. Their service is top notch, their rates are very fair for the service they provide and you won't be caught off guard with any hidden charges or "fine print" that will have you scrounging to pay your bill at the end of the month. I only wish I would have found them sooner so that I wouldn't of had dealt with months of pure hell with the other incompetent hosts who did nothing but damage my site.