I found that the Maschine was great fun, but I never actually got round to playing a live set on it (partly due to moving city and not having an oppurtunity to play live much, partly because preparing for a set using Maschine would take many weeks, and there seemed like a lot could go wrong).
I just play around on it at home now mostly, I use it as a VST in Ableton or Fruity Loops for producing, or just plug it in on its own and have a jam, building up a tune on the fly is super fun.
I found it wasn't ideal for production on its own, a little clunky - works much better as an add-on to a DAW. I'd recommend getting one though, there are some cool tutorial vids on youtube with good finger-drumming techniques, after a couple of weeks of practice you can really get some great sounding rhythms out of it. Plus you get the NI Massive synth free with it.
Just bear in mind integrating it into a live set can be tricky, and take a bit of preparation.
Yeah, I've heard that trying to get Maschine and Traktor cooperating nicely in terms of syncing MIDI clocks and so forth can be a bit of a pain. Hopefully a future update to both addresses this. Friend of mine was looking at adding me in to a band in order to drop samples, but got a bit stuck trying to figure out how to do it properly to keep things in time.
Have also seen a couple of videos of a guy called Bass Kleph using it in conjunction with his DJ sets, using them for live remixes of his own songs, so can definitely see some awesome potential in it.
I've heard there were issues with the S2 and S4 USB plugs failing on a few people. The X1 Mk2 and Z2 I have have been fairly reliable to date (touch wood).
I had an S2 and S4, but not a Native Instruments Maschine. Have you tried searching for opinions on Google?
Yeah, reminds me of a video where David Guetta was DJing on a morning TV chat show without the mixer being connected to anything.
I'm going to ask on DJ Tech Tools as well, but thought I'd canvas a few other places for opinions as well. Couldn't really hurt to get as much feedback in this case.