I like it overall, but I do disagree with a few things.

I would phrase Ridiculous Velocity as "You gain a +1 feat bonus to speed. Increase this bonus to +2 at level 11, and to +3 at level 21."

I would consider reducing the base speed to 8. You already have Ridiculous Velocity to increase it, and I think it could get too high. We're not even factoring in items. If you do reduce this, it may be fair to give Quicklings a new/improved racial feature. Quick and Speedy could give a +3 bonus, for example.

I agree that Agile Retreat is too good, perhaps make it 2 squares instead of 3.

I think this is a good race with potential to be very useful.