I think that counts corporate developers, and corporations are not switching to Vista yet. And anything you write for XP will port to Vista, so there is no reason to target Vista specifically. To port to Vista, you may have to add a manifest file to your software and possibly rewrite some parts like installer scripts, rethink some of the flow of the program due to user prompts that might popup and scare the user, and update documentation to warn users. But developers had the same problem of having to test in Windows XP separately from Windows 2000 and Windows 98 when XP came out.

Microsoft's own latest software remains compatible with Windows XP, and while Vista is one extra operating system you will have to test for, Virtual Machines let you run multiple operating systems on one computer.

That's not to say I miss my Vista system that I ditched for my mac. :)

My recent experience with Vista has been hell.

It virtualizes c:\Program Files for "compatibility" so that you can see bizarre situations like writing to a file and then having it not exist where you thought it was.

To avoid these virtual store problems, you have to embed XML in your application's executable to get the infamous ALLOW or DENY window to bother the user. If you use Visual Studio 2005 to do it, watch out! There's a bug in a certain class of unpatched XP that blue screens the computer because of the way the XML is structured that Visual Studio's manifest tool spits out when it merges manifest fragments. It's all overly complicated.

I would never develop Windows software if there wasn't a market for it--it's exciting to see the underdogs picking up marketshare.

Give it time. The computer manufacturers are no longer supporting XP. If you buy a Dell now, you have to get Vista. So before long everyone will port over to Vista.

Not that surprising. Two years ago I was a fulltime commercial desktop application developer, and our minimum supported spec was Windows 98.

This statistic is misleading. All those xp developers could be making vista-compatible programs without specifically making vista the primary target OS.