The omake is really cute and great in a very silly way.
Also I love how the mangaka draws all the characters that were killed at the end of each volume as angels floating towards the sky.

As for the actual series itself it's really addicting. Also I was really shocked when the identity of Pride was finally revealed. (manga, not the first anime series) I'm not even going to put it because you would be tempted to look at it.

And Gluttony is adorable when he's not going crazy or anything.
(SPOILER)Hues's Death plays a really big part in the Manga.

But you should either watch the second anime (brotherhood) or read the manga. You get to experience Ling