I am in this club as of last Friday when I received two CZ Jenna Tessars M42 50mm 2.8s in a consignment together with a Spotmatic II.
As they took a while to be delivered I spent a lot of time exploring other people's experiences. I realise that they may not be the most fantastic but at times can be surprising.
Both are rather stiff to focus and one had sticky aperture blades and the other had a couple of spots on the lens coating that tends to flare when facing into reflections. They are freeing up nicely and the aperture blades came good with a q-tip and acetone via the rear mount and the rear lens group. One of the two lenses was not specifically listed by name and focal length and I was hoping that it might be a Flektogon as it is by far a better lens and I don't have a 35mm prime at present so congrats on your purchase.
This are two of the first pics - the very first few were exploring the functions of the lens as it operates with a stop down lever rather than having the A/M switch like my Takumars and Tokina.
Converted from using ACR and resized in PS CS3 only.
As I was reshelving them I realised I have acquired 5 50mm-55mm lenses by seeming osmosis :->.
Cheers, Arjay