Originally Posted by kranou
so do boots stack? like if i got 2 sets of boots would i then have lvl 4 movement?
No, however if you got Boots 5 and Boots 3, the Boots 5 would occur first since it has the most.
Then you get hit by an enemy champion, the effect drops to 2, and then the Boots 3 would kick in and be the top. It's not really worth it, because you're getting about 32 movespeed for an additional 1000 gold and an item slot while out of combat.
(32 because you're probably at or above 450 with the boots 5, and it gets a 20% reduction so the bonus [of 40] would get reduced by 20% of that).