I have just shortened my chain by half a link so I can switch between a 16t and 14t cog for road/track useage. For the 16t this moved my rear axle about 12mm forward. I could not believe how much this changed the handling of the bike: It is quite a bit more responsive now.

However, I do have a pretty individual bike with 24" (yes 24, that is not a typo) wheels (see link below). Do you guys get a big change in handling on the 650 and 700 fixies when you change the position of the axle in the dropouts?