People banging on about WINE
Yeah, having used Linux for a few years now, I can tell you that while WINE is rather bloody good, it's not a miracle fix; try running XenCenter on it. Fat chance.
Also, try running your proprietary XP software on it [name any package you need paid support for] and if it works, wait for it to get a bug.
Then call up your software vendor, and listen to them laugh heartily when you go through a certain set of steps, at which point the app crashes due to WINE not behaving exactly like an XP platform, and refuse to support you for running it on an unsupported system.
The best way to migrate to a *nix platform is to find a FLOSS alternative that runs natively on DistroOfChoice, or to rewrite your apps for it, if you can. Some apps transfer better than others - web apps, natch, and anything based on an open-ish platform that can cross compile, some basic .net apps that will run with Mono and so on.
If you can't do that, you're basically stuck if you actually want to have proper support from your vendors and suppliers.
I'd also be interested to see how large vendors who haven't updated their software to run on Win7 deal with support requests for software running in XP Mode - I'd put a fiver on them desperately trying to get out of it if they can.
It's not right, and it's not fair, but it's the way it is.
For what it's worth, I'm no MS apologist - I have four machines here, three running Ubuntu, and one Xenserver box. I also have a Win7 VM for 'emergency' access - such as when my good chums at openxencenter update the SVN and break the Python XenCentre clone and I need to fluff my VMs. I like my Linux, but alas, the idea that you can just magically transfer to Linux in a corporate environment is closer to fantasy than it is reality at the moment.
Ah well, maybe one day, eh?