Depends on the device! (and the software it'll work with)
Some are better quality than others.
Although, most of it is down to how you encode it at the PC end. Given that the source material is very low quality (comared to what a PC is capable of producing) you are always going to be limited as to how much 'cleaning up' of the resulting digital video you're able to do. If you give it a grainy, jumpy old VHS recodring, you'll end up with a grainy, jumpy digital video!
Any graphics card with TV in is capable of doing this by the way. It's not a new thing, been graphics cards and USB boxes around for years allowing you to do this ...