Rockpile: as speed increases (getting closer to the speed of sound), a deer's time window to react shrinks. Below is a chart that outlines the time (at various bow speeds)between a deer hearing the sound of your bow going off, and the actual impact of the arrow.

Just so you can actually see how the speed gains will really help you. I thought it was interesting...

fps 100 150 200 250 300 350 400
yds T I M E
10 .27 .17.12 .09 .07 .06.05
20 .54 .34 .24 .18 .14 .11 .09
30 .81 .51 .36 .27 .21 .17 .14
40 1.08 .68 .48 .36 .28 .23 .18
501.35 .85 .60 .45 .35 .28 .23
60 1.62 1.02 .72 .54 .42 .34 .27

Now, I'd argue that a deer can not possibly jump the string on a 250 fps bow at ten yards. That's about 1/10 of a second. If your bow is shooting 400 fps, in that same timeframe, you can ram an arrow through the the target from 20 yards away.

So you ARE gaining something.