I love 'em! I've had two (well, I had one and my son had another). Mine was an '83 and his was an '82 but they're identical except for graphics.
The good:
Light, flickable, very 'satisfying' torque and response of the 500cc single. Super fun on backroads, around town, and commuting. Nice enough on the highway, too, but can get pushed around by wind. And of course, you might be cramped/underpowered a bit two-up on the highway... Two highly-recommended mods: go up a size or two on the pilot jet and main jet. Makes more power, starts better and actually gets better mileage! Then, go up one or two teeth on the front sprocket. Slows the motor down nicely for 55+mph riding, and with the power that comes from the jetting swap, you still have power available.
Ours never got less than 55 mpg on my daily commute or my son's riding either. All speed-limit 45 ~ 50 surface streets and stoplights.
The bad:
Yep, you've hit the two issues. They had a tendency towards top-end oil leaks at the cam cover joint to the head and they could have gimpy starters because of a gimpy 17-separate-gears-and-shafts reduction design (or so it seemed...)
Mine suffered both, but my son's didn't have either.
However, the fixes are easy and well-documented, and once done, the problems don't re-occur. At least, mine didn't.
All in all, I'd recommend one in a heartbeat! In fact, I wouldn't mind having one again, if I happened across one... :-)
Good luck, whichever way you go.
Kirk