i've got one, it's in the shop right now... just go over it carefully before you buy it... rust is a big thing, especially on the rear wheel wells/arches
yes the clutch does require engine removal, and it's a bitch. many shops won't even work on the car, so it can be hard to find a competent mechanic sometimes.
other than that, it's awesome. mine is currently undergoing a rally spec engine upgrade, with a bunch of other goodies. i think i posted a few pics a while back somewhere on here.
some common problems/things that need replacing/have been overlooked by previous owners... some of the tranny/diff bushings, the struts, the wheel bearings... oil leaks will also a problem, especially with those high mileages, if the gaskets haven't ever been replaced.
also some things to consider... it gets worse gas mileage than the supra (the awd), and it's a totally different kind of car. the supra is a great high speed car, you can go 100 and it feels great. the alltrac was made for low speed driving, stopping and starting quickly, and low speed cornering on rough/bad surfaces. the ride will be much much harsher, no matter how you have the suspension set up. it feels like a rally car, because, it is, not a touring/track car like the supra.
all in all, in my opinion, the st185 is one of the best cars toyota ever made, and the WRC titles prove it. i love the style of the st165, and basically all the same issues apply to both models... the st165 has even less creature comforts than the st185 though.