We work closely with a colocator with an office 2 blocks from FDC in Chicago. They have one awesome business, and if we were in a position to do things like that we would in a heartbeat. Support is our concern as well; I certainly wouldn't rely on Dell. We could otherwise make a two hour drive to set up new machines.
I know FDC has had awesome colocator deals, but a lot of data centers don't. I think it all depends on the deals you can find. Unfortunately FDC supposivly only has room for 100 more machines right now

. It would certainly feel nice to own your servers outright though if a data center will give you a good deal.