for just having fun, not competing? i'd say the 490 could be a effing hoot.
i had one that was my primary off road bike... tight single track, mountains, woods, desert, sand, snow, everything. it was a very fun all-around bike. it wouldn't have been competitive in the tight stuff, but i wasn't competing... it was still fun. in the open stuff? it was a monster and competitive. the bike, that is... the rider (me) fell off too much to be competitive.
i sent the jug/head to Eric Gorr for the "head mod" and stated that i wanted low rpm grunt. what i got was a much, much easier starting bike, easy to jet, didn't ping, lugged like a tractor at idle and would rip when demanded. there wasn't a huge hit when it came on the pipe... just more and more thrust feeling.
the forks had race tech gold valve cartridge emulators, sent the rear shock to race tech for their treatment (seem to remember that costing around $500, years ago).
i put an IT flywheel & stator plate on it, a headlight & tail light. don't remember if it was just a drop-in affair or not...
i even rode it on the street reasonably often (usually just connecting trails).
there are bikes of the same era that are way, way easier to ride in the tight stuff (IT175 comes to mind)... but there's something to be said about coming to a clearing, cracking the throttle open and hitting warp speed while throwing a roost of rocks the size of softballs as you hang on for dear life, grinning from ear to ear.
damnit, i'm gonna go find another 490 now...