...Are the adapters any good? Do they work....?
Technically, they are not "adapters". They are, instead, "mounts".
The T-2 system is an interchangeable mount system. The lenses are designed to function when a mount is attached. They won't mount on any camera without one. As a result, the "mounts" work very well.
There have been several variants of this particular interchangeable mount system and there have been other systems. The T-mount system is based around lenses that have a 42x0.75mm thread at the rear with a 55mm register distance. The original T-mounts were single piece solid machined pieces. As the system expanded with multiple sources for lenses and mounts the mounts evolved into the T-2 mounts. These are the current style and are made in two pieces. Loosening the grub screws around the outside of a T-2 mount allows you to rotate the two pieces so that the lens' scales are properly aligned at the top. The original T-mounts had no provision for such alignment. The T vs T-2 distinction applies only to the mounts; the lenses aren't different and are properly referred to as T-mount lenses.
The T and T-2 mounts have not provision for coupling the iris to the body. There is no auto-diaphragm stop down and no meter coupling. Most T-mount lenses are pre-set lenses, others are true manual diaphragm or fixed aperture (e.g. mirror lenses). The mounting system is currently popular with astronomical telescopes and has been used for various accessories like microscope adapters, slide copy attachments, bellows, and the like.
There was a short lived mount system called the "YS" mount that was based on the T-2 mount and added auto diaphram and, in some mounts, meter coupling. It used the same 42x0.75 thread with the same 55mm register. It wasn't very popular and had a short run. Vivitar also had a run with a ruggedized T-mount line (no T-2 style alignment provision) for some of their early Series 1 Solid Cats. These lenses and the matching mounts had a standardized thread alignment so adjustment wasn't necessary. If you use one of these mounts with a conventional T-mount lens the scales on the lens could face at an odd angle.
Other interchangeable mount systems have had their period of popularity. Tamron had their Adaptall and later Adaptall-2 systems. There was also the T-4 and later TX system used by Soligor and Vivitar for a number of years. These all provided meter coupling and auto diaphragm with support for most popular camera mounts in their day.
There probably have been others I can't think of right now. None, though, have had the long life (over a half century at this point) of the T/T-2 mount system.
