"You may end up buying a few until you find the one that works well."
Nah, there's no need to do that. You only need to buy ONE. The trick is, go to the Microsoft web site and find the hardware qualification list ("HCL") for your operating system. That's a list of all devices that have actually been $ubmitted and te$ted and confirmed to work with that OS, at least most of the time.
A "logo certified" USB-to-serial adapter may cost $5 more than an uncertified POS from China, or it may not cost anything more at all. IBM and Keyspan are two of the companies that have had certified adapters for years now, I'd expect anything that had a Vista certification will also work under "Vista-dot-one", which is sold as Windows7.