A few days ago I acquired a
Tamron Adaptall-2 SP 80-200mm f/2.8 LD (30A) and so far it seems quite good.
Wide open there is a bit of spherical-aberration induced glow - especially at 200mm - but good detail. The glow decreases and detail increases upon stopping down.
Purple fringing is noticeable, but CA is not bad at all.
Max magnification is approximately 1:5, which is not bad for this sort of lens. For comparison, the Pentax DFA* 70-200/2.8 is about 1:8, the Sigma 70-200mm F2.8 EX DG OS HSM is also 1:8, the Tamron AF 70-200/2.8 Macro is 1:3, and the Tamron SP 70-210/3.5 19AH is 1:2.66.
+ Pentax A 1.4x-S Rear Converter, minimum focus distance