It's not an action show. At all.
Come now 'Kishi, the anime is pretty close to the manga right up until the end when they decide to randomly mess with some stuff. And it's pretty. Very, very pretty.
Anyway, regarding L's voice, didn't sound terrible. It's my preference that Light has a deeper voice than L, given how the original Japanese was done, but it works pretty well I'd say. Just need to hear it more.
Light's English voice actor definitely nailed the crazy, which is good since he's going to need it.