6"3'ish and around 240# and I fit easier than in my Saturn SL2.
Another thing to remember about the Smart is that it's much higher than most cars, so it's a lot easier to get in and out of. I pivot myself in, then brace my left foot on the floorboard provided for that purpose and arrange myself into position, then reach behind me to grab the elusive seatbelt, LOL.
Because the car is narrow, the only real issue is when you have a passenger: you have to take turns buckling up.
