I guess I've probably transcribed as much drumming as anyone. There have got to be some other lunatics out there, but not that many, and they're not publishing their work regularly. In this past 9 years of cranking this stuff out, I've noticed some patterns in people's playing.
Caveat: There is a bit of selection bias: I only transcribe things that are transcribable— a lot things can't actually be written out, or written out in a reasonable amount of time. I don't transcribe a lot of hardcore-crazy performances, but I do things that have a greater than normal amount of drumming interest— something with the groove, comping, fills, or soloing. There has to be some element of improvisation. Most of what I transcribe is from the 1950s-70s, and most of the rest of it is from the 80s-90s.
What I've noticed:
People don't use their left foot that much
I'm always surprised at how much left foot activity there isn't on most records. Jazz drumming usually calls for a more active left foot, but many do not play it on arranged sections of a tune, or when soloing.
They don't necessarily play a lot of tom toms either
Plenty of things only have the toms in one or two spots, or not at all. Often the guy never makes it down to the floor tom. Relatively few things that are not Latin tunes have lots of toms throughout.
Hell, they don't even play the bass drum that much
I view the drumset as a complete four-limb instrument, so I'm often surprised that there are still drummers who do most of their playing just with the sticks. Some of these cases may be jazz players feathering the bass drum constantly, and it isn't audible on the recording. To me that's functionally the same as not playing it— I'm more interested in what people play for effect. And the bass drum is often used for effect very sparingly.
Nor do they necessarily hit a lot of different cymbals
A lot of the things I transcribe may only have two cymbals on them, and they often don't make it over to the left side much. On the few recordings where a China cymbal is present, they're usually not wailing on it throughout the tune.
Lots of people have little hiccups in their soloing
Not just extra beat of rest, but actual moments where the drummer loses the thread, and the beat evaporates for a second. It happens when you're improvising, following your ears, and letting your hands do their thing— sometimes your ears and hands just fail for a second. These older players were not fully working every single thing out in the practice room— they were mostly playing constantly.
Increasingly in recordings since the 70s and 80s, the best known drummers are more practiced, editing performances has become possible, and standards have evolved, and I hear that less often.
They have idiosyncratic ways of playing rudiments
They often get severely slurred, squashed, messed around a bit, especially on recordings from the 50s-60s.
Funk fills often have bass drum in them
And I don't mean as a modern linear thing. A lot of people will step on the bass drum under a heavy tom tom fill— just a steady rhythm, Gene Krupa-style. Especially in 70s funk.
Transcribing with a program like Transcribe!, it's easy to highlight a bar of music, and drag the selection forward when you're ready to transcribe the next bar. When you do that, it's easy to see that not every bar of music is exactly the same length. Also plenty of things recorded before there were click tracks rush or drag over the course of the tune, and tempos may change on different sections.
People play both more and less repetitively than you might think
Most people, when playing, are not focusing on how to work in more of their stuff. They may not have a huge variety of stuff worked up in the first place. Some performances that sound pretty varied have surprisingly little actual variety. Other players are constantly making variations, but it still reads basically as a repeating groove. It's weird.
Dynamics track the song
On a level too subtle to notate. Jazz drummers are expected to be very sensitive about dynamics, but I hear the same level of sensitivity on older pop and funk records— it will be very obvious that the drummer is really listening, and his dynamics are shifting subtly to support a phrase or vocal line. It's important, because a lot of people think pop/funk drumming = whacking a backbeat at a perfectly even volume.
There is not that much fancy stuff happening
Much of it is just not that technical.
There may be a lot of semi-intentional notes happening
In writing out every single note audible on a track, I've written a lot of unplayable transcriptions. Some of these things are like archeological sites, tracking the body motions of the performer, and obscuring the intended musical performance. It may say something about a player's physical attitude towards the instrument, where they're throwing a lot of motion at the instrument, and so a lot of extra stuff is sounding that wasn't necessarily intended.