Here's what I know (in a nutshell):
I don't know if the switch to Intel makes it inherently easier to port apps from Windows to Mac, but it definitely can't complicate the process.
Now, if/when a new version of VirtualPC comes out (I don't know how VMware and others work, so I can't comment), it will makes things run better since VirtualPC runs Windows inside an environment of emulated hardware. Having a main component in common would make it much less crappy.
Games, depending on how they do their fancy eye-candy, could be cake or a nightmare to convert based on what technology is used to render everything (OpenGL vs. DirectX). Most games are written with DirectX in mind because apparently it's easier to work with, but is only available for Windows. Some things, like Doom3 (and from what I can tell, WoW), are written in OpenGL, something available across platforms.
In other words, if something is written for Windows in OpenGL, I can't see how it would be very difficult to convert for use on a Macintel. This depends on how much is OS-reliant, something I don't know at all.
Hope this helps clear things up a bit.