unless you really own an alltrac & work on it yourself, i don't feel you can comment on it honestly. i'm not a big fan of hear-say.
if you get one, make sure the body is free of rust & make sure it has had important maintenance taken care of on a regular basis.
you will hear a lot of people say they aren't reliable. if kept pretty much stock with regular maintenance, they are reliable -- the probs come when you add mods & kick up the boost on a motor that is 20+ yrs old then the reliability flies out the window.
as far as parts availability, some OEM parts are & have been discontinued by Toyota. what do you expect though? there were never that many alltracs made (165 or 185) so Toyota has no interest in continuing to make a part they may sell 10-20 units per year.
since the 3sgte was available in MKII MR2's engine parts are no problem, just unique alltrac parts become a bit more challenging - be ready to be persistent.
in conclusion, you better be willing ready & able to work on the car in any & all kinds of weather & you better have plenty of tools & a BGB.
an alltrac can be quick, but you better have some deep pockets to get it there.
as much as i love the car, there are plenty of newer cars that are a lot faster & take a lot less to get there.
if you're willing to make the commitment, good for you, but it's not for the faint of heart ... i can say that honestly.
to the guy above that said ST185's are oogly, i'd be willing to bet money you've never seen a real one in person else you wouldn't say that