OK, I realize from a previous post that it in a previous post it may seem like I think that windows is completely non-functional in a cloud environment.
Let me back up a little...
From my perspective, running production servers on virtual machines spun up on demand is not useful (yet) with the windows operating system. The windows OS strategy is just not responsive enough to this sort of business requirement (yet).
That having been said, I just finished spinning up a windows 2003 server instance on rackspace... Why? I need to investigate some Active Directory problems we're trying to solve at work right now. I spent 4 hours downloading the massive DVD install image (and a bunch of crazy MS registration stuff) for a 10 day TRIAL version of the OS.
I then went over to my rackspace account (because of a different problem) and realized they could set up the server I needed. I clicked "create server" and they set up a virtual server in 15 minutes. Yes, it costs more to run this server than my Ubuntu instances, but it's only going to run for a couple of hours over the next 2 days so I don't really care.
In short, on-demand virtual windows machines (I'd love some XP/Vista/Windows 7 instances for testing our software hint hint) are a super useful thing and are worth their weight in gold (maybe even platinum), but this doesn't mean it's a good distributed virtual server platform.