Well (this could get to be a long post)...
My subway heritage goes back to early childhood riding Lo-V's etc. with my Mom and Dad from Newkirk Avenue to Borough Hall IRT. But my primary experiences date from my first real railfan trip - July 27, 1963. From that year through 1968 we had an annual "subway day" - railfan trips all over the city. After August 3, 1968, the trips became much more numerous until I got my wings on February 3, 1971 (the "wings" meaning official permission to ride solo from Elmont to wherever). During 1973 and 1974 I commuted via N6 bus and "F" train to Manhattan (Lex-53rd).
As for riding in the 60s and 70s - there were tons of wheezing, creaking R-types (R-1, R-4, R-6, R-7 and R-9), especially on lines like the "E", "F" (yes, they were there), "EE", "GG", "CC", and later discovered to have completely infested the entire Eastern Division (except for R27s/R30s on the "QJ"). The last of the BMT Standards were sputtering out (we saw the last one, on the "M" on our August 4, 1969 marathon trip). Slant R40s were new and exciting, especially the air-conditioned ones. And R42s were starting to make their appearance, the first fully-air-conditioned fleet. Some of our late 1969 trips were spent seeking these cars out. Every line (except for the "HH") had at least one train of them. Air-conditioning was a novelty and a blessed relief (especially in the summer). In 1972, the first R44s appeared on the "F". I just missed one at 47th-50th one day and rode clear to Coney Island just to ride it back. One of the cars I rode that day was #140, later to be renumbered #5282, and later still to suffer a horrible fate at 135th Street. By early 1973, they were in full evidence on the "F" line, and the R-1 and R-4 cars were for the most part gone. R-16s replaced R-6s and R-7s on the "EE" and "GG". R-6s and R-7s moved over to the "CC". The one thing that I miss most about the 60s and the 70s was the faster express runs. Today, with all the GTs and modifications, you're lucky if you get above 45MPH even under a full green (although I DID get lucky on December 11th aboard an R38). Flourescent light in the IND was a rarity - you only saw it in midtown (some mezzanines still cling to the ancient bulbs, especially in Queens). On the IRT, yes, there were Redbirds, but without rust. There were Redbird predecessors like the R17, R21 and R22, and also cars like the R12, R14 and R15 about. Whole trains ran mixed consists. In fact, the entire IRT, with the exception of the Flushing #7 and some solid R17 trains on the #6, was one big mixed bag. The #8 line gave up the last of its Steinway WF Lo-Vs in 1969 and acquired R12s. It gave up for good a few years later. The oldest cars running were the Q-types on the "MJ" (Myrtle Avenue El, which ran until 1969) and some of the last BMT Standards, a couple of which ran on the Culver Shuttle and the "LL" and "M". R32s ruled the "D" train, as well as the "AA" and "B" trains. R10s were still just about the only thing you'd see on the "A", except for the occasional R42 and the even rarer R-4/R-6/R-7 mix (which was what they usually ran on the Aqueduct Express).
By the mid-1970s, the R46 began appearing and the last R-6/R-7/R-9 cars were withdrawn by 1977. Slant R40s moved over to the "A". Deferred maintenance set in. Graffitti was everywhere. The decline had begun. It wasn't until the mid-1980s that things began to improve.
Wayne