Edit: Done a Zürich-Madrid flight with A320 FBW with no other addon, and it was finally a smooth experience apart:
- ATC constantly misjudging my altitude
- AP suddely deciding to veer off course upon approach towards a mountain (i.e. had to land manually)
- on exit to main menu and monitor the font size in the main menu went 2x smaller
Glad you had a (mostly) smooth experience finally. Shouldn't have to re-install, but... it does seem to help.
I think SU5 knackered people's installs rather than being an especially buggy update in itself (which has been largely fixed anyway through hotfixes, but that won't solve an already broken install). That's the impression I get, reading around.
I am happy to report that here the autopilot (without any manual intervention whatsoever) is still broken, so I can still crash into mountains or land 10 miles from the runway and it tries to go the remaining distance on the ground (kinda). I was slightly concerned that they'd fixed that hilarious bug with this update, as some kind of kiosk mode for the Xbox version in stores. But, no.
At some point, I will clear some space on my desk and break out the HOTAS again so I can do a proper flight.