Really, he's not. His tilts are al faster (yes they are. especially the utilt), the fsmash can be strung at least as quickly as in Melee, his fair is clearly faster in attack speed seeing as how there's a good chance both hits will actually connect (and it has a smudge less start-up lag), and his running speed even has a faster animation in addition to the increased speed (it's not a very big increase, but it's noticeable nonetheless). Hell, even his arrows and boomerang fly faster (his fully-charged arrow is one of the fastest-flying projectiles in the game in fact). It's just that speed in general isn't as big a factor in Brawl as it was in Melee (that's Brawl 101, sure, but it can't be stressed enough) but fundamentally, Link's speed has gone from sluggish to only slightly below average.