Don't be put off by the "Made with SynthEdit" badge, as Aly James has gone above and beyond SynthEdit's base offerings to faithfully recreate the FM sound of the Yamaha YM2612 that can be found in the Sega Genesis (Mega Drive in some regions) of old.
Using the official documentation collected and translated by the folks at SpritesMind Forums and verified with hardware tests, the FMDRIVE is not only the most accurate sounding YM2612/YM3438 virtual instrument on the market today, it also has a very nifty looking interface that should properly evoke the nostalgia one would expect from seeing a Model 1 Sega Genesis. There are also some (literally) under-the-hood features for controlling the sound of the FMDRIVE, including choosing a "high-quality mode" that should work with any given sample rate in a DAW and some "circuit-bending" that applies some "interesting" effects that may or may not be possible on a real YM2612.
Aly James has also added the ability to import YM2612 presets dumped directly from game music to quickly recreate the classic sounds made legendary by the Sega Genesis such as Sonic's ring sound effect and the slappingest synth bass this side of a DX7, and has graciously provided for free download a collection of over 30,000 of them from various games! Even Yuzo Koshiro himself loves the FMDRIVE.
I'm a YM2612 fanatic and have been studying the chip since 2005. I also have a small bit of programming experience and have tried and so far failed at making a YM2612 virtual instrument that even comes close to the sound quality and user-friendliness that the FMDRIVE offers. Compare the sound of the FMDRIVE and an actual Genesis side by side (Aly also provides YouTube videos doing just that) and tell me if a virtual instrument comes closer to the sound of the original console than FMDRIVE. 10 Euros (I forget the actual conversion to USD, Paypal handled that) is a small price to pay for professional quality Sega Genesis sound excellence and I'm glad I paid.