While certainly not as common as the garden variety Rolleis with 75mm or 80mm lenses I don't think the tele-Rollei is actually very rare. On the other hand, the wide angle Rollei is a little bit harder to find.
The tele-Rollei does take a very nice photograph though. Probably the biggest downside is that it can't focus up close. I don't remember exactly what the minimum focus distance is but I think it is around 2 to 2 1/2 meters.
You gotta love a fast lens;
It is almost as good as a fast horse!