is it worth supercharging an engine with 85 thousands miles on it, or does it depend on the condition of the engine

Oh yeah its worth it... Performance wise that is. If its been a smooth 85 Grand, then the rods and bearings should have had a nice wear in.... but if its been rode hard and hung up wet, ( I dont know whut it means either) Then your ring seal may be deteriorating... either way you will eventually have to rebuild the engine... as long as you keep your boost down and the super is properly tuned, i.e. ~ timing, air/fuel, no detonation, etc, then you should be safe. but when you do decide to rebuiled, forged pistons, lower compression, billet crank, and main stud girdle. just to name a few.
Hope this Helps,
~*Adam*~