I own both A-Bolts and Tikkas. The A-Bolts that I have are the original A-Bolts, not the newer A-Bolt IIs. I have been told, and I don't know if this is true, that the newer A-Bolt IIs are not as good as the original A-Bolts.
Anyway, both of my A-Bolts are Stainless Stalkers and I bought them back in 1989 and 1990. They are in .270 and 7Mag and both shoot like a dream.
I don't know about the internal mechanisms, but I think that the quality is definately there. Have I ever had any problems? Nope. In fact, I have used them through very tough conditions and they have never let me down. Don't get me wrong, I too have heard that the A-Bolts, or at least the newer ones, are "over engineered." But still, I have never had any problems with them.
As for the Tikkas, well, they truly are very simple and high quality rifles.
Zachary