The Opsix is the latest addition, besides my Korg Prologue, Moog Grandmother, Roland JV1080 and was intended to full in the open position for an FM synth. Having owned the original DX7 in the past, I can honestly say the Opsix is fantastic. It can do anything the DX7 can (although not all patches from the DX7 translate well to the Opsix), and so much more. The effects really add something to the FM sounds, having a filter is amazing compared to the DX7 and the intuitiveness is great. I was able to get started without reading the manual, it all makes sense.
I have give. 4 stars for finish because the keybed does not stand out as other reviewers also have mentioned, although it is not as bad as some people claim it is.
All in all, if you consider a great bang for the buck and if you are looking for an intuitive FM or VA synth, do not hesitate and get this fantastic instrument