The engine is good to go. I like it. Has great midrange punch and decent bottom end.
Maint./Reliability is mostly fixed on the later year F800s (after 2009ish). The big issues with the bikes prior to that were the stator burning up (around 30 or 40k miles) and random failures of the rear axle bearings which IMO was being caused by a way to tight belt spec by BMW. The stator was fixed with a redesigned stator and rotor which helped with cooling which was what was causing the stator failures. The rear wheel bearings were fixed with redesigned bearings I think.
As long as they carried over the "fixes" to the GT model it should be good to go.
2004 Suzuki DL650 Weestrom
1978 GS 1000
"Those who would trade security for a little temporary safety deserve neither liberty nor safety."