We have 12000 miles on our 2013 ERA 70A since May. Agree with the lack of insulation. I added some wherever I could. We use a plug in inverter from Walmart for keeping electronics and other small stuff charged. I use the power point in the rear intended for tail gating and run a 110v extension cord to the inside bed. When traveling there is always some electronic toy being charged. It also powers the satellite receiver when not plugged in. The TV and other electronics are 12v.
We do not use the pie slice shaped cushion to make the twin beds into a king sized bed. In the space by the refrig where this cushion is stored we had a roll out pantry made.
As with most RV's, there were rattles and squeaks. Patience and me using a piece of hose to my ear while the wife drove found most of them and all have been fixed. If you buy it and want info on what noises seem to be common to the breed, PM me. All are fixable.
The in dash GPS on ours is a disappointment. Too hard to use (the wife says diabolical). I think they changed it for 2014. I would make sure I knew exactly how to use it before I left the dealership.
The sprinter heating A/C controls are a bit different and take some getting used to, but once understood are great and work extremely well. We did have rear and side door screens installed in ours. Huge improvement, but pricey. The side window sreens do not completely stop bugs. If you need more info I can give you a simple cheap fix.
All in all, love the unit. We plan to keep it for the rest of our RV'ing days. 18.5 MPG, love the genny (LP), lots of lights, plenty of storage, some would disagree but we love the bath/shower.
Good luck!