Yes, I change ISO a lot. Depending on the lens used, it will have a known 'sweet spot' in aperture and since so much of what I shoot professionally has to be very high resolution and readable, with the Canon's I can go way up the scale and still get what I need.
I won't tell you the first PC I worked on but you can extrapolate one of the few choices, perhaps, from this, the first computer I worked with extensively was a DEC VAX 700 with an additional 128k of memory and a 64k Matrix Processor. I worked with digital imagery on the first Mac's and on the Lisa (anybody know what that was??).
As part of what is arguably the first full micro controlled TV station, I lived with IBM PC-AT serial number ... 32.. for nearly a year. Had number 34 as the test unit for switching software. This was 80286 technology. Lots of cool video gear floating around at that time. Now all that stuff is beyond primitive.
One serious advantage, even with early DSLR's was not having to carry two or three bodies just to have different film loaded. Even with noise issues it was a big step.