This is one AMAZING anime and it is #2 on my list of favorites! ( Second only to Clannad and After Story)
Angel Beats! is hilarious, action-packed, and very sad and touching in certain parts of the story. If you liked Clannad but wanted a bit more action, this is the right anime for you! If you liked Clannad and was fine with it, you should still watch this anime!
Like Clannad, Air, and Kanon, Angel Beats! has other arcs in the story containing stories about the characters' pasts and it allows you to grow closer to the characters. You can get easily attached to this anime and the ending will definitely leave you wanting a second season! All I have to say is that you should grab a pack of tissues for this anime because some parts are quite touching, but it is mostly full of action and comedy!
Wish you a happy Watching!