I've never had any concerns about the Zero and it's turn. Outside of the Ki-43 and Ki-27... the A6M Zero in all variants was considered an excellent turn fighter and it had almost no equal in close in fighting.
Such was the disadvantage that other fighters had that tactics had to be developed to defeat the Zero. USN pilots developed the Thach Weave to counter the Zeros incredible horizontal turn rate:
http://en.wikipedia.org/wiki/Thach_Weave