For the money the lens is going to be hard to beat and from a few shots I have seen compared to my Canon 100-400 they stand good comparison.. I dont know what the A700 is going to be like for noise at higher ISO as this will be one thing to take into consideration at shooting at 6.3 at the 400- 500 end of the zoom

Danny O'Byrne  http://www.digitalartzone.co.uk/

"All the technique in the world doesn't compensate for the inability to notice" Eliott Erwitt