I have to say I'm quite enjoying my OPL2LPT that I got earlier this week. Was doing some testing/playing around with it on an XT clone system using software I wrote and modified to use the OPL2LPT instead of the 0x388 port. It worked on both the standard parallel port on a Hercules clone card (0x3BC), and on the port on the Multi-IO card at (0x278). Can't quite compare the sound with a proper Adlib card as I only have a SB Pro 2 (OPL3) in my XT, but the sounds are very similar, with a very good amount of punch.
I also have been doing some testing with non-PC computers, and currently got the OPL2LPT working (playing a tone) on an Epson QX-10 CP/M based system. Seems like it should be fine to connect, and write software for, on any system with a Centronics compatible printer port. The Epson uses a standard 8255 for the parallel port, and the code ended up looking remarkably similar to the x86 code for driving it. Just needed a cable adapter (comprised of a standard printer cable with the micro-ribbon end in the computer, and a gender changer on the other end) to hook up the OPL2LPT to it.