OK it's installed (XP-SP3), and as others have already noted, there are some subtle but big differences in text appearance. Looks like they optimized letter appearance at the expense of spacing whenever push came to shove.
a little dodgy at times. Primarily in web browsers (FF and IE).
But for everything else I'm looking at, I think I like gdipp's rendering more.
Verdana's lowercase M likes to 'crash' into most following characters, but it doesn't pose a problem for reading purposes.
Text rendering, like most things, is a series of trade-offs. I guess it all comes down to what looks best to you.