While not with 8 differing aircraft, my own Dx6i has been a great starting tool for getting into this hobby (even if it was via a 3D capable nitro heli) - not one single glitch in almost 2 years, though I do run on a 6volt Nimh battery system to ensure I don't get any brown out issues re low voltage off a 4 cell 4.8 volt pack (I don't like the idea of 2cell lipo's and voltage regulators, too many links in the chain to go wrong IMO - K.I.S.S!!)
Still, now that I have a desire to get an engine governor on my heli, and with my planes run more control options and functions on my P51 (nine servos in that puppy, 10 if I add a choke system on the gasser in it), I'd like to have a higher spec radio with 8-9 channels, for simple things like variable servo speed on flaps/retracts etc - cannot get them adjustable options on the Dx6i, just on or off.

So on personal experience, if I was to offer one bit of advise, buy the best system you can afford or justify spending time on saving for, it will save you money in the long run that's for sure!