did you seriously just ask if pronation affects your times?
http://www.youtube.com/watch?v=EAW87NsiGuI
if you dont already know, that right there is haile gebreselassie, often said to be one of, if not the, greatest distance runners ever. and that is what a running store clerk or even a so called "biomechanics specialist" would call some of the worst pronation they have ever seen. and yet he's never had any notable injuries other than some minor pains associated with the amount of work he does and the intensity he does it at. pronation doesnt affect you in any way, its just your body's way of absorbing the shock, and everyone has different ways depending on size, weight, speed they're moving at, and the way they land when they run.
and in regards to the store you go to using "high tech cameras and equipment to tell you what kind of shoes are best" thats comeplete horse shit right there. the best shoe for you is the one that you feels works for you and feels right.
if the greatest runne rin history doesnt have problems with pronation (as well as one of the other all time greats, kenenisa bekele shown at the end of the video here:
http://www.youtube.com/watch?v=dKMZfYn6e80&feature=BFa&list=FLuC5hqqhjtqc&index=2
) then that right there should tell you it wont affect your times.
if you try to correct pronation, more often thne not you'll end up hurting yourself. what you should be focusing on is how you land (is it on your heel first, or the forefoot, or even midfoot?).
as long as the heel isnt landing first your fine. pronation doesn not cause injuries, its heelstriking and overtraining that do. some people tho (like desire davila and shalane flangan) are able to get away with it with either little to no problems (in desiree's case, altho she does use lighter shoes with lower heels to my knowledge) or problems every now and again but otherwise fine (shalane's case she's been injured a few times at the end of the year but has gotten it under control for now). but those are cases where they have access to things you and i dont (therapists, whirlpools, shoes whenever they want, nice trails or tracks to run on, etc). and you can get waay more mileage out of a shoe if you run efficiently (i.e. forefoot or midfoot, not heel first) and injuries or nagging pains you may have clear up quickly (ive met people and experience myself that once they changed ther biomechanics to a forefoot/midfoot strike even if they (or even myself) had a naggin issue or injury right then and there, it would immediately be alleviated (my case was a hip issue).
dont buy into the whole "pronation is bad for you" crap and that you need to correct it. as soon as i did havent had any issues since.