I just got my new AP2 712s last month. I was fit by a Titleist rep who also recommended I go 1/4 inch longer, but due mostly to the fact that I tended to grip the club very much at the very top. He thought the extra 1/4 would allow me to grip down to where I should without feeling any loss of length. Frankly, I never thought about it again, but have been hitting the new irons VERY well and have not noticed one iota of difference in the length. I am however hitting it a few yards longer with the new clubs and absolutely love them. As far as controlling the extra length, it's a non-issue.  At least it has been for me.

I have my irons +1/2 and I think that is not very apparent....+1/4 and +1/2 are almost identical...IMHO

I have always played +1/4-1/2", simply put, I think I hit the ball more solid gripping down, but I'm actually taking a grip where I was fitted to. The pros always talk of gripping down to flight the ball in the wind which usually makes you hit the ball more solid, i often grip down a quarter on my woods also, I feel this helps in maintaining my grip better.

Always get fitted outdoors using a launch monitor by a good fitter. That is how you will find your answer!

FYI -- Titleist research by the R&D team tells us an additional +1/2" length with a 6 iron will hit the ball about 1-1 1/2 yards furtther. However, a 1/2" off center hit can cause a 5 loss of distance.  Just like everything else in fitting .... a longer shaft might produce a SLIGHTLY longer carry, but off center hits are much more costly.

steve ball
Sr. Consultant to Titleist Club Ffitting since 1992