I only have 7.1Mbps DSL at my house, that's going to be going to some Fiber optic, but YouTube is loading up pretty quick. Sure, around the afternoon and nights when those big corporate T3s and fast internet lines are tearing at their servers they make take a minute to load or to do a search, but they've been loading very quickly lately. Before Google bought YouTube, they were very slow, half of the time I'd have to let the video have 2 minutes to even buffer enough for me to watch it without a stop. But that doesn't happen any more, and I can even use the &fmt=18 trick to get higher quality videos and it doesn't take a dump at all.
I'd say run a trace route to YouTube if they're slow. It may show where the slowness is occurring if it isn't their servers.