Hi Vincent,
It definitely sounds like you're going for the higher end of the market, so I'm not sure how much my experience is going to help you.
I'm mostly hosting the hobbyist / small company / community / developer without DSL / developer whose cable company bans servers segment of the market. The folks I have are pretty happy with command line, and really like having root access on their virtual servers. They're comfortable making decisions about which mail server to use, etc, and don't generally need much from me. They want to be able to customize their environment, recompile AOLserver at a whim, install stuff, and then host it all on a fat pipe for cheap. :)
I suspect there's also a high-end side of the market that wants managed services on servers they own, but I couldn't really tell you exactly *what* they want, or at what price point. They've got to be out there, but I don't know what they want. I do get the occasional query from someone looking for really managed services, but that's not really what I'm marketing. I guess the question for you if you want to do the high-end managed co-lo is: what do you offer that other co-los don't? A reliable back-up solution that gets all the database files intact might be one answer...
BTW, I'm actually making money, although it's true that I'm not making a living on it... yet. I just need to scale up a few orders of magnitude first. :)
