For $529/mo I got:
2x Intel Xeon-Clovertown 5320L-QuadCore [1.86GHz]
4x Seagate Cheetah ST373455SS (10K SCSI drives)
Hardware RAID controller
16GB RAM
2TB transfer per month.
100Mbps uplink
Peace of mind
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 )
About a year ago I spent many hours talking with a rep who came back with the same boxes and prices we could have configured with their online system.
Last week I spent a couple hours chatting with a rep for userscripts.org's new box and he did better than the online prices.
I think the difference last year I approached with general requirements, so they spent all their time speccing out multiple systems and figuring out what was the best fit. My second experience I knew what I wanted, so I was able to ask for deals based on specific hardware choices.
http://www.softlayer.com/specials.html