CMK is a "hodge podge" of quality.
They issued a series of German armor by combining old Tamiya kits with their own parts and some PE. They had a Bergpanzer IV, a Bergtiger, an Ostwind, and a StugIII late. The additional parts which were supplied were crude at best. They were molded in a soft white plastic with crude detail. The original prices were on the high side ($50). They have since then been marked down and can be found occasionally for around $10-$20.
All of the kits were based on the Old Tamiya versions, not the new retooled kits and as a result suffer from the problems in the older Tamiya kits. The PE was not enough to cover the whole kit, so if you wanted to do it full, you were going to have to purchase another set anyway. I've not seen this series of kits for quite some time so I am assuming they are now out of production.
The CMK volkswagen series and their Pzkpfw 35T series are buildable kits. And to my knowledge are the only ones of these vehicles/tanks in plastic in 1/35.
CMK also has a line of resin kits. These are made in conjunction with Airmodell. Therefore, the quality is the same as Airmodell.
No, they aren't all bad, but you do have to be aware there are some dogs in the line.