The E39 didn't have any crazy quirks. They ironed out most of the issues in the V8's. The rest of the car is just normal E39 issues. Watch the 540's in the E34's as there were 2 V8's and the early one didn't make much power and doesn't have as much aftermarket support. The later 4.4L V8 is by far the better option. My personal favorite is the E39 540T sport. I found a guy selling one with a 4.4L 6 speed swap and the M body work. That is the sex, but I like sport wagons.