The DX6i (I have two) does have one problem area that can bite. It's setup to use either conventional AA cells, or rechargeable NMIH batteries.
The individual battery contacts can get dirty and cause intermittent operation. It's easy to cure by cleaning them every now and then.

I'd prefer the DX 8 or a Futaba 8FG. Features beyond those of the 6i make either preferable. The DX 8 has some interesting master slave configurations, and can use a DX6i as a slave(so I'm told)
At the moment, I'm also in the process of assembling the "RTF" version of the Hanger 9 P-51. Problems so far have been fitting a set of 60-120 electric retracts, finding the exact size and width wheels needed, and locating the proper size spinner. The Hanger 9 RTF version's spinner was discontinued as a replacement part.
The E-Flite retracts have a peak current draw much higher than the 900ma listed in the specs. As the retracts start to move from the retracted position, the current draw is in excess of an amp, and will cause an AR600 or other receivers to see voltage low enough to cause the LED to blink. This is using a 4 cell 2000ma NMIH. This behavior is overcome with a 5 to 6 volt 3 to 6A BEC, preferably separate from the receiver/servo power source. During "normal" gear travel outside the detents, the unloaded current draw may be around 300-500ma or less.

An example of NMIH "A" 2700ma cell behavior is attached. AA cells have a lower current capability, likely less than marginal if electric retracts are used.
Shims may be needed with the E-Flite retracts to properly position the gear in the retracted position, or thinner wheels used.