Keep in mind that the L saga is itself separated into several parts.
We have...
Spoiler for Warning, LOTS of spoilers:
1. The Exposition: Light receives the Death Note.
2. The Battle: Light meets with L and joins the team.
3. Yotsuba: Light forfeits his note.
4. The Ending: Light kills L.
If you try to adapt this into the full series, you realize that it makes for a very, very crappy series. Why? Because the Yotsuba guys suck. They're boring. They're stupid and lack any real character. They never reach the level of "OMG COOL" that Light and L reach. Not only that, but because their saga takes sooooooo long, you're left without the single factor that makes Death Note so compelling: the battle of wits between Light and L. Not only that, but I think it's generally accepted that L's death is fairly anticlimatic. While Light's plan was absolutely genius, the way in which L dies is just sorta... meh.
For this reason, I'm hoping that either they do a FULL faithful adaptation of the manga (I've not read past the introduction of L's successors, though hearsay tells me the second half of the story is pretty crappy), or a retooling of the storyline to minimalize the involvement of Yotsuba and shorten the amount of time Light spends without the note--because let's face it; an honest Light is a boring Light.