I'm running a (still working) Sun unit I bought in the early 80's with dwell meter, compression gauge and remote starter; Craftsman is ok but ....
...now I'm waiting for the "what's a dwell meter" questions...
I mean.... you really only need one if you are running a points distributor.
They are nice to have for diagnostics on most distributors, because they can tell you if their is an issue with an ignition control module or trigger that would otherwise be hard to find.
They are completely useless on a modern car, since the dwell is set in the computer and is dependent only on the coil part number.
It's interesting to note that dwell is one of the biggest benefits to going CNP on a modern engine. Most points distributors tell you to run ~28-32 degrees of dwell timing. Most primary coils need AT LEAST 2.5ms of dwell time to achieve maximum charge on the coil. At 5k RPM, 2.5ms takes 40 degrees of timing. So, if you have a single ignition coil, you have to short charge the coil in order to allow all cylinders to fire. With individual coil packs, there is ample time to get a full charge on every coil even at 7k+ RPM.