Often when a non-car person drives my 89 900, they remark on how much fun it is to drive. I believe this is because of the double-wishbone suspension and front geometry, which cannot be replicated with struts. Also, the axles are nearly equal length, so torque steer isn't bad.
Maybe I'm too attached, but I've not yet driven a newer, sharper car and wished I didn't have a 23-year-old Saab.
I used to run the stock 89T on street tires in autocross. You can put tons of camber in with shims (I also ran an 86 with so much camber that the tires hit the springs unless they were on the ground; the car easily oversteered from the front grip). It's got a lot of torque when the boost kicks in and you won't dominate anyone but I had a helluva good time running it.
My friend and I TSD an 85T. We took it on Alcan 5000 and ran it to and on the Arctic Ocean in Feb. We ran it deep in the boost for hours at a time on that event; she never hiccuped. I'll be running it at a TSD this weekend up in B.C., where it will almost turn 300k miles, original bottom end (cross hatches still visible at 250k). It has a Quaife, is lifted a bit, skidplate, "boxed" control arms, and lifted SPG springs, but that's really about it. We cannot seem to kill it. It has thousands and thousands of miles on gravel and snow. Yes, it's rattly as hell now, but is quiet on the highway, and drives quite nicely to/from events.
I think that it's certainly possible to have the gearboxes last, but my experience with six or seven 900s is that you're odds aren't good (all had issues, from bad synchros [83, 86, 92] to pinion bearings [86, 89] to outright destruction [85]). The best ones are from 89 and 90s, second best are from 91-93. I currently have two rebuilts and I change the gear oil every 20k. Both get different flavors of Redline, as the transmission acts as a big heatsink.
Finally, my car recently made 200 whp on a Mustang dyno; stock is 160 crank. You could do the same for about $20-$50 and a day, depending on your pick-n-pull's prices. More is achievable without considerable effort.
EDIT: My car has the STUPID passive seatbelts, too. Lucky for us, though, every other market had standard belts, so you can replace the passive stuff; the fastener points are all in the car. Note, however, that the belts have to come from an 88-89 base model 900 3-door, or 87 and earlier hatch -- not positive how far back, but probably at least to 83. (In '90, they went to a different buckle shape.) You'll need the interior panels from the donor car as well, or you may be able to carve out holes in the existing panels (the standard belts' reels are behind the panels, with a pass-through hole for the belts). There's a FAQ on Saabnet. If you are OCD, then you'll also replace the headliner, which is different on passive-belt cars.