Good on you for bringing it up!
For me, tooling around mountains at 10,000 is no problem.
IFR in a big machine is fine. It's the little buggers at alititude that feels so flimsy and "squirelly". I had the opportunity with an instructor to go up to 10,000 in an R22 - thankfully the winds were too high and we canned it. I KNOW I would have hated it.
FW at FL350 is no problem. You're mainly concentrating on drinking coffee and finding the best winds anyway...