Brought along my new (used) TC14E I to test at the track (Not that I need it for any reason, I just wanted to test its AF and Image Quality under regular shooting conditions. Have to say i'm incredibly impressed, I used it only with my 80-200 af-s, And I Didn't notice any hunting or slow lock or anything, In fact Because of the distance I seem to be taking pics at with this, I seem to keep the rider in focus even easier now! Heres a few examples of quick moving bikes approaching me, and AF-C mode on my D50 trying to keep up (And doing it easily!) Impressively sharp in all the pics aswell, I can't notice a difference wide open (or even stopped down for that matter). Thanks for looking!