Just having 1 issue after the 10.6.3 update though (screen stays completely dim after putting it to sleep most of the time - have to put it to sleep using the task bar at the top and wake it again for it to brighten)
i'm running leopard, which itself runs a ton better than tiger on my 2ghz macbook white [2006]... seen tremendous improvements esp. in finder and spotlight speeds
sl is faster than leopard, so I doubt you'll have any issues with speed