I've owned my 909 for over a year now, and I have to say, its the best mixer I've ever used, I don't make use of more than 2 channels, so didn't want a big club mixer type, and started looking at 2 channels.

As far as 2-channel mixers go, this is definatley amongst the best out there, I went for the 909 simply because it is superior in customisation, the touchscreen gives you full control and view of fader curves and effects, effects can be assigned to work on auto BPM or manual bpm (you tap the beat using a small button). The faders are solid and very smooth, as are the EQ's, which have a large range.

The effects are mind boggling, there are 50 effects built into the mixer and are totally unique to the 909, for example the fader flanger whereby you adjust the effect by moving the volume fader for that channel!

Effects are channel assignable which can make for interesting mixes.

Has all the usual inputs/outputs, but there's one thats very usefull called "session in", this is used when your having a battle or back2back DJ sessions with friends, whereby you route the output of their mixer into the session in of the 909 and gets routed to the output of the 909 so you effectively have 2 mixers playing at the same time. If your that set on the 909, you could even get 2 909's, link them up (for example, you could have 1 with decks attached and one with CDJs) for a full 4 deck setup!

Its a solid mixer, well built and will last a lifetime if treated well.

I got mine secondhand for £330, so thats a fraction of the £750 price tag! There are better sound quality mixers out there, but for effects, customisation and layout, the 909 comes out top for me!

that "Session In" facility sounds like a clever way of wording an Auxilliary input?

I guess you could think of it like that!

If you have 2x DJM-909's, you can route the session out of mixer one to session in of mixer two and it balances the volume for you so both mixers are set to the same volume which just ensures that the output from mixer one isn't louder at the speakers than mixer two which could happen if you individually setup both outputs to input to an amp.

Its slightly more clever than just session in when you use two 909's, when you use any other brand mixer then yes, its basically an AUX-In port that you have no control of the volume for that input other than the setting the output volume of the connected mixer!