The usual fault with the clone adapters is apparently that the screws holding the mounting spring work loose, causing the spring to jam. They're not generally as well machined though - they've reverse engineered the K mount rather than having Pentax's drawings and measurements.

The only Takumar Bayonet lenses worth touching are the 28mm and 135mm f2.8. I've heard reasonable things about the 70-200mm f4 zoom too but it's really a case of "only buy if stupidly cheap", given that you can find the full fat SMC lenses for not much more.