Is anything harder to program than a Yamaha DX7? Sure! the TX-81z. This is a less fully featured digital FM synth. You would think less operators means its easier to wrap your head around, but the user interface is not up to any tasks you set out to accomplish. These units are a glorified ROMpler without a dedicated PC program to navigate the terrifying FM synthesis landscape. That said, once you grok FM synthesis and your 3rd party software the TX is a pretty decent device and its quicker to program than a DX. And its small and easy to slave to your DAW. It records really well. Really fun for making nasty percussion noises and Depeche Mode Violator-era FM bass stabs. I think this odule sounds better than a dx7 through a guitar amp and/or distortion pedal. I've never had any issues with the buttons or jacks on this unit but she's been mostly babied (as in not taken anywhere and barely used).
Compared to VST FM Synths this unit has balls. Only the overall volume in the output stage is some low. No matter of that, i run it to the mixer and raise the gain with the preamps. Somewhat complicated to edit the sounds. Control it with midi cc out of the DAW.