I played this keyboard for about 1.5 hours at a music store, seriously considering buying it. I was comparing it to the Korg N5EX, didn't stay with the n5ex for long, I quickly switched to this instrument. The piano samples on the Korg were lousy. In comparison, the pianos on the QS6.1 are much fuller, richer, they very good immediately, although they probably could be refined with some editing. I liked the semi-weighted keyboard action very much, doesn't have that light springy feel like the Korg. The user interface, unfortunately, was much clearer, and seemed easier-to-use at first on the Korg.
The sounds: The pianos, EPs and organs are very good. So are most of the synth sounds. Some of the fantasy sounds are amazing. Some of the acoustic instruments are not so good, the guitars for example. The strings were okay as I remember. The drums... I couldn't find a decent acoustic drumset, the electronics are good, but the 'real' ones sound like a they're from a cheapo GM module. All in all, this seems to be an excellent instrument, it could have some more acoustic sounds. There are (sample ROM) expansion options, which is good. It doesn't have an arpeggiator, however, which is included in most snyths at this price range... but you might not really need one.