My biggest grip so far would be the waveform knobs. They have a bit of wobble and don't feel like they're up for the long haul, but that's also me being my usual negative self. It would be awesome if someone comes up with a full on screen editor for it (standalone, MAX or whatever). To be able to fully patch edit remotely would be huge. I'm using a Kontrol S25 for my purposes, but I'm not even remotely any type of "player"... I play the DAW and/or sequencer.
Very happy to have a hardware monosynth again and can't complain about the sound at all. At some point I'll pick up the Behringer D, if for no reason the collectibility, but I'm almost inclined to get a 2nd SE-02. Waiting to see how much of the honeymoon phase wears off. Whether or not it's for you... YMMV.