I tried the Keylab 88...for about a week! All the buttons and sliders were in the perfect position for me so on paper it is the perfect keyboard for me. The keys do thump a bit, but on-stage with foldback you can't hear it. However, after I got it home, I noticed a couple of stuck notes, but thought that was a problem with the software setup. Alas, I was wrong - after a few days, the top 8 notes stopped working. I took it back - while another one might be ok, I didn't want the same problem to happen out of warranty in a year's time or whatever.
I have since instead gone with a Roland FA-08 (extra $ but it only weighs 16kg so similar to the Keylab), and I'm very happy with it. The keys are better to play, and if you don't use the 'DAW Control' mode, you can actually link the all 16 drum pads to different functions (DAW mode sends CCs from the bottom 8 drum pads only while normal mode sends 16 MIDI notes on midi channel 10).
The key differences are that you only get 6 knobs rather than the sliders (but I don't normally control more than 1 parameter per synth per song so 6 is heaps), and you have Roland's joystick thing rather than a pitchbend and mod wheel. The joystick isn't quite as good as a normal pitchbend wheel but I have learnt to use it, and for me, the benefits of this keyboard outweigh this small drawback.
Also the drum pads aren't pressure sensitive but I don't use this function anyway.
To summarise, for me, the Keylab has the features that all these keyboards should have, but I wish they'd built it better. The FA-08 has stuff I don't need (workstation sequencer etc) but I can use it as a MIDI controller and sound card so overall it's much better for me.
P.S. I recently did a gig in another state where I was using an old and battered rental Roland RD 700 which seems to be built along similar lines to the FA-08. It seemed to have stood the test of time so I'm hoping this one does too!