(That is the question...)

Ok, so from when I got the bike, the tachometer (rev counter) didn't work.  The needle just lies on 0.  So I though, something's wrong with the cable.  Yet, not that simple...  Apparently, the whole little motor that drives the tachometer wasn't there.  No problem - got that motor, but now couldn't fit it, as the little gear on the camshaft that drives that motor is all chewed up and simply wouldn't turn the motor.  I guess, that's why it wasn't there in the first place.  There's also quite a bit of free play movement about the camshaft, which produces some rattling noise when moving at low speed (no rattling at idle or at high speeds though).  The point is: to get this fixed, I'll have to get a new camshaft (hopefully, everything else is working there).

The main question to answer is: should I bother or not?  The bike is a '97 GS500E with 43K miles on it.  I fixed a couple of minor electrical things (changed flasher relay and voltage rectifier). Apart from the camshaft issue, the bike is fine.  Rides great, doesn't burn a lot of oil, etc, etc.  Worth adding that I use it for daily commute to/from work - about 35 miles each way, about half freeway, half city.  Also, I got virtually no money to spend - but who does?

So, should I bother or not?

No, instead you should simply replace the gear-driven tach with an electronic one if you really want a tachometer.

Does the tach gear run off the exhaust cam?  I never looked.  It is on that side. 

Is it just lateral play or actually wobbling around in the bearings? 

Yep, it's the exhaust cam.
And, yes, there's some wobbling.

So.... you're buying an oversized cam and milling the journals?
Or, just slapping in a new one and calling it a day?

End play in the camshafts is a known issue with early GSs. There's noise at idle, but that isn't actually a problem mechanically. Later ones have shims to correct it, but you can't fit them to the early ones. If the camshaft has excessive play due to wear in the bearings, there is no (Suzuki) fix except to replace the head! Maybe a machine shop could line bore them and make inserts....??
If your shaft is OK apart from the tach drive gear, there are plenty of electronic tachs around which would be much simpler and cheaper than buying a new camshaft.

I wouldn't call it excessive, just some play.
Overall, considering the mileage, it's ok (about 45K miles now) - and it drives fine (except for the noice at lower speeds).  I think I'll just skip the repair for now.  I've been ridiging with tach at 0 for the past 2 months - will keep doing it.  Either I'll ride it into the grave (hopefully, it won't ride me into the grave ) or I'll sell it and get myself a newer bike, if I get enough money saved for it (oh, the dreams... I suppose, the mortgage will always come first - or at least for the next 13 years).