I know this is an HP forum, but the history of this stuff affected the whole market.
TI did do some amazing things.... the modules for the TI-59's, the nearly 1000 program steps, and even the ability, figured out by users, to do synthetic programming. I also played yesterday with the speed, and it still blew away the 15C and other quite slow calculators.
I've also been able to resurrect almost all of the 59's I've bought. The SR-52's are so much tougher to get the drive roller right, but I've even gotten that down to a "science".. (using rubber faucet washers, "turning" them on the drive motor with a dremel to the correct diameter.)
Despite the lack of a plastic barrier, the corrosion doesn't seem any worse than the HP's, actually. I suspect that the plastic barriers did little to prevent the corrosive action of the gasses. Sometimes it even seems that the coated copper circuit boards survived better than the solder-traced HP's circuits. (Though the "clean" HP's are still a wonder to look at!!)
STILL, even with the fact that I programmed the 59 all through college (in fact, every program I wrote for class I duplicated on the 59 and it did alphanumerics), I HATE programming it, compared to the elegant HP-67. Sorry, even with years of AOS programming, it doesn't come as naturally to me as RPN.
It's fun to compare, though. And the history is understandable, but sad, why the HP's didn't survive. It's been discussed many times here.
As a collector, it's an amazing history.
Michael