The 707 has a number of features that are really attractive. But I think the main question is... what functionality are you trying to gain?
I have MegaSeg on my machine, but only use it for literally queing up a playlist I want to run. It auto-gains itself well. It fades between tracks. You can certainly map midi to it... and while MegaSeg will take the jog wheel input, it's not really set up for a mixing DJ to do a lot of manipulation. So the DJing side of it seems almost entirely unncessary.
However, this unit in particular is a better than average mixer for a wedding DJ. It's got zone control, feedback suppression, as well as reportedly good mic preamps (I've never heard them personally).
Those might be reason alone to use a unit like this. But I would assume it is replacing another mixer that is currently in your lineup if you use it that way.