If you really want something that is peace-of-mind, you should just use something like rightscale.com. We have a giant ad server on there load balanced across 40 ec2 instances running perl code, seems to work well so far. Sometimes an instance will get fussy and we'll just create a new one from scratch by running scripts that essentially fetch everything needed from CPAN and installs, configures, and boots in one step. It's definitely a more expensive solution, but if you want peace of mind, that's probably the way to go.
For $529/mo I got:
Sure I could get everything but that last item for less. There is an inflection point where it is more economical to run my own hardware again but I'm not there. For a few hundred more than cost when issues occur a competent support person is helping me within minutes.When (not if) there are issues with my servers, driving to a colo would eat my savings. When you have a hardware issue at softlayer they fix it. They don't have to wait for new hardware as they have a stock.
I'd rather be spending my time coding and working on features. Having your own non-mission colo-ed box is awesome, but the cases where dedicated leasing or AWS doesn't make sense are fewer and fewer for bootstrapers.
Note: userscripts.org is 3 years old. It ran on a colo-ed box for a year. Then a $200 serverbeach box. But it just outgrew that ( http://userscripts.org/articles/22-2008-overview for 2008 review with stats )