the ds8 is only 4-op vs the dx7's 6, and there are less (well, only 2) algorithms available compared to the many on other similar 4-op synths a la the TX81Z, dx21, etc... Although it is very similar to the TX81Z in that is gives you other waveforms beyond sine to start with, still still more limited.
But on the bright side, it is substantially easier to use than any of these (tho still quirky). Nice big backlit screen, and all the functions right there in front of you, and there are even a couple of realtime sliders (but which only work in performance mode, and whose values can't be saved-you can only do that on the little brother, Korg 707).
Also has great sounding and editable delay FX unit which dramtically (or subtley) improves what can be very dry noisey sounds. I am a big proponent of these simply because you can get really weird sounds out of them pretty easily, and they are well worth it for the price. the keyboard is also velocity and aftetouch sensitive.
If you wanted more "authentic" FM programming, and a wider range of sounds, I might go for the TX, or one of the other yamaha FM incarnations.
Do you even post on vse bro?