NLE's are bloated programs that hog the computer's resources. Vegas and Premiere love to suck up vast amounts of RAM and CPU, as well as write swap files to the hard drives, and that can interrupt the sustained data flow needed for DV capture. Interruptions can reveal themselves as errors in the video.
Don't worry about the age or development status of good software. Windows XP dev is stopped, but it's a great OS.
DVD Decrypter is stopped, but works great. Age has nothing to do with quality of the program.
Ignore those forum posts for now. Try it on your computer, and see how it works. As I sometimes tell people, "your computer won't catch fire if the program decides not to work". Most all XP programs work in 32-bit Vista. The only WinDV/Vista problem posts I see online are for the x64 version.
Sony is big, but their software is not without its issues. Not to mention Sony has only owned the software for about 2-3 years now, having bought out Sonic Foundry (original developers of Vegas). If anything, it became more of a resource hog in the hands of Sony.
Sound Forge is the same.
DV transfer is a 10-15 year old process. There's nothing "more current" to be had from any software. Recent versions of Vegas mostly support HD video, embedded more effects and native codec support -- little to nothing will have changed for DV support or DV import.
You also didn't quote the full reason for WinDV dev being stopped. "Development of WinDV has been stopped.
DV format is getting superceded by MPEG4 HD video, so further development of WinDV makes no sense for me."
Indeed, DV is as dead as VHS.