That era is a little bit before my time. My first SLR, at age 16, was a Minolta SR-T 200 - which had manual, match needle, open aperture metering, like a K-1000. But of course, at that time Minolta already had their three-mode XD-11 on the market, and Canon had the A-1 with a program mode too, and a digital readout.
But you're right, the progression of those features, like open aperture metering, took the 35mm SLR a lot closer to being a serious tool that challenged the supremacy of the Leica rangefinder.
In only a few short years, the 35mm SLR evolved from something like the Exakta, with its pre-set lenses (remember to stop down before you shoot!) and non-returning mirror, to the Asahiflex with its instant return mirror, to "automatic" lenses that closed and opened with the shutter, to TTL metering. It was a pretty rapid pace of change, and it all took place in about the same number of years we went from 6 megapixel to 16 megapixel digital SLRs!
But hey, don't forget, that upgrade path is a slippery slope. Today you're discovering the joys of open aperture metering, but before you know it it you start wondering about aperture-priority automatics, then TTL flash, then autofocus, then digital.
And before you know it, you'll want your old Spotmatic back!