Pioneers
PROS: The only CDJs I ever feel totally comfortable with... even down to the CDJ100s. Setting up cue points is straightforward on all the models (although the actual process varies). The balance of the jog wheel on the 800 and 1000 models is great.
CONS: Expensive! The cheaper models (i.e. not the 800 or 1000) can be a little sluggish - I don't trust them for dropping tracks in from a standing start.
Numark Axis series
My favourite "budget" choice... responsive, nice rubber buttons. I find setting cue points tricky, but that's probably down to the fact that I've never sat down with one to work it all out (only ever used them in the heat of battle, so only time to check the basics).
Denon
Can't remember the model number I've used, but it's one of the spinning platter versions. These are the best I have used for scratching (basically like scratching a 7"). But the platter is belt drive, so as soon as you let the track run you're back to mixing with belt drive turntables - pushing and pulling tracks in the mix using the platter is awkward and unreliable. They provide +/- buttons for nudging but that's a cop-out. Also, the interface was unnecessarily fiddly... you have to press and hold buttons and wait for lights to flash to access certain functions, for example.
I've never used on of the Technics CDJs. They look great... but there were videos online at the time of launch which showed some serious flaws with the audio when manipulating the pitch. This could well be fixed by now.