Like you, I needed the same thing to run a device that worked off the printer port, which my laptop didn't have.  I tried one cable USB to parallel that didn't work, then bought a USB to serial (the device had a serial port as well) and had some problems getting it set up, but it finally worked.  I still have to tweak it every time I use it.

So, yes, they sometimes work, but sometimes they don't.  When I posted here about the problem, I got some good advice, some said they had no problem at all, some said they don't work at all, and some said that some brands work and some don't.

Maybe you will be one of the lucky ones that has no problems.