I picked up my first Digital body (Canon T4I) a few months ago after a lot of years shooting and processing 35 mm film. Because I have a large number of Canon, Tamron Adaptall 2 and Sigma lenses with the Canon FD mount, I wanted to try some on the T4I. I did not want to switch out the Adaptall mounts because I'm still using the various lens on my A1.
I picked up a FD to EOS adapter to try them out on the new body (keeping the old bodies and still shooting film also). One thing to note is if the adapter does not have the glass element in it, it likely will not focus to infinity when in use with an adapted lens. In my case, I have to manually focus and stop down the lens as the camera will not do that for you with these lenses. That may or may not apply if you replace the existing Adaptall mount on a Tamron lens a replacement mount.
I've only tried using the adapter a few times and I find it's difficult to accurately focus using the view finder, definitely easier using the split screen viewfinder in my other cameras. I find I have a lot better results focusing if the subject falls into the infinity range of the lens. My adapter has a ring you turn to stop down the lens for the shot when you're ready to take the picture, otherwise it stays at maximum opening.
That's my results so far, yours may vary. Good luck