1) For THIS singer, the PA800 harmonizer is much better. The add-on board did not come close to the smoothness and blend that I get with the PA800.
2) Clumsy - it's been a while, but that's the only woirld I can think of right now. There were things that didn't feel natural to me. Can't honestlt say what they were.....piano sound was thicker, the cutting off of certain sounds...the inability to switch between song and live mode ..... little things like that.
3) weight - well, with all the extra poundage, my 800 sounds better than the pro speakers. That's personal, of course, but if the manufacturer says it's better...I guess their UNbiased view is the truth, right?

I just love this thing, and I would not trade back for the 1x for any money.