If I'm being honest, I haven't made great use of the T981 since buying it but here's what I discovered so far.
I've used a lot of different rangefinder cameras over many years including both fixed lens types and ones with interchangeable lenses. A few I've liked, many I haven't and I came to the conclusion a few years ago that rangefinders were not really for me. So I'm a little surprised I like using the T981. I think it is partially due to accepting Shin Yasuhara's concept of 'all you need' and not immediately thinking about getting extra lenses etc. In fact, the viewfinder only has frame lines for 50mm lenses so any other focal lengths would require a separate viewfinder - something I particularly dislike. The lack of other frame lines might be seen as a disadvantage by some users.
Another positive for me is the 1:1 viewfinder. I've not used a camera with one before and didn't expect it to make any difference as I'm left eyed so my right eye is blocked by the camera and keeping both eyes open or not makes no difference to me. But, still, the 1:1 viewfinder seems more comfortable to look through. I'm sure other, right eyed, users will like it if they prefer to keep both eyes open.
The camera is quite heavy compared to other similar cameras. Caused, no doubt, by the brass top plate and metal knobs and other parts. The viewfinder also uses solid prisms rather than thin lenses which must also add some weight. I weighed my body to be 530g (the specification says 500g). With the Yashica lens that increases to 713g. A Bessa R2M body, as a comparison, weighs 430g. I don't find the weight a problem. It weighs a lot less than my Sony A7ii and a bunch of lenses. Your mileage may differ (as the saying goes).
One of the complaints of the T981 is the visibility of the metering LEDs. They are positioned in the viewfinder within the image area and are difficult to see against a bright subject. The green LED especially. I've written more about this in the Modifications part of this site so won't repeat it here but, even with my modification, the LEDs are still, sometimes, difficult to see. Some rangefinders that use lights in the viewfinder to indicate exposure place the lights outside the image area. This makes them much more visible. I have looked at repositioning them on the T981 but that's maybe a modification for the future. In the mean time, I've got into the habit of putting a finger from my left hand over the part of the viewfinder where the LEDs are. This makes the LEDs easily visible in any light. A simple but effective solution. Update: I've now fitted a small piece of adhesive tape to the front of the viewfinder to cover the position of the LEDs. This has the same effect as putting a finger in front of the LEDs and makes them more visible but without the inconvenience.
The rangefinder is clear and effective in a wide range of lighting and I have no problems with it at all but see what I've said about the rangefinder in the Modifications section as it was the biggest problem with the camera when I first got it. I can't say that other examples will have the same problems but it's definitely something to look out for if you're thinking of buying a T981. Other people have complained about the stability of the rangefinder and the difficulty of adjusting it so it isn't just mine, but it may not be all examples. I've addressed both of these issues with modifications.
The viewfinder has a surround with grooves and the size appears to be the same as on Yashica/Contax cameras so eye cups and correction lenses for Yashica or Contax should fit. I found a Minolta Vn correction lens also fitted inside the surround although I don't currently use it.
I've fitted a 'softie' release button to mine. I think it makes a big difference and it's something I generally do with all my cameras. The shutter release is slightly lower than the top of the shutter speed dial and they are quite close together. Fitting the softie brings it above the height of the speed dial. As an aside, on the Yashica FX-3, where the shutter release is identically placed, the release button stands above the height of the speed dial making it less of a problem.
Some users have complained about the noisy film advance. It makes quite a loud ratchety sound. It's caused by the ratchet that has been added to act as an anti rewind mechanism but also a wind lock once the film has been wound on. This had to be added, compared to the Yashica FX-3, as, with no mirror box or mechanism to operate the wind lock, an alternative had to be made. The basic mechanism is similar to that which can be found in other cameras, but it is a bit more noisy than some. But not as noisy as others. Try the Konica Auto S2 for instance.
I have to mention the unusual film rewind crank. As a marriage of parts from different cameras, the T981 suffers a little because of it. The rangefinder takes up a little too much room and other things had to change to make room for it. One of these is the rewind crank. There was insufficient room for the rewind knob to sit beside the rangefinder housing so the rewind shaft was split in two and geared together so the upper part could be offset from the lower part. Sounds like a good idea maybe but poorly executed. The gearing between the two shafts is coarse and not very well made, adding friction and resistance to the rewind. Add to that, the rewind works in the opposite direction, due to the gearing, and it's not great. I did add some grease to the gears which has helped but it's still difficult to rewind a film.
There has been reports of the shutter on the T981 allowing light to pass through. Yasuhara-san accepted this could be a problem as the shutter is designed for use in SLRs where the mirror blocks much of the light. His recommendation was to keep the lens cap on. I did test mine and found no light leaks through the shutter but I have seen what appears to be a light leak on a few frames coming from somewhere else. This needs some more investigation and I'll update this site once I've done that.
Despite some shortcomings, overall, this is a rangefinder I like and, unlike several that have come and gone before it, I think I'll be keeping this one.