Personally as a Japanese mahjong player, it is at the extremes of "unrealisticness"; having Rinshan-Agari almost at will [refer to Saki -Portable- PSP Game in wikipedia]. But when it comes down to simply enjoyment, I'd say a pretty good anime.
Story: 8
Simple but coherent and well-structured (may be because I read the original manga in Japanese) it has a story and a goal that Kiyosumi Kou-kou aims at, and seemingly intense mahjong uplifts the atmosphere with players giving away some ulti-rare yakus. Sub-stories about relationship between the girls fits in quite well with the story as a whole. Points are lost from showing too much about second season in the last episode, which hasn't come out in 2012 as well! [At least OVA is coming out and looking forward to that]
Art: 8
Modern graphics and Anime Designs seem flawless at least to my point of view. Bits of points dropped at bad background and some colour flaws. Not much to say here.
Sound: 7
Voice acting seems to fit well with the Characters [Kana Ueda, voice actor of Saki Miyanaga, is actual mahjong player] and sync themselves well with the character's emotion but some points dropped from BGM which sometimes didn't fit in my view.
Character: 6
Couldn't give a high score since I personally did not like any character in the Anime, except Hisa Takei. This is one of the parts you guys will have to judge on [I am not "moe moe otaku", so speak for yourself]
Enjoyment: 10
As a mahjong player, it was well, indirect satisfaction from the anime. Just looking at Saki's Rinshankaihou and Koromo Amae's Haiteilaoyue [believe this is the correct Romaji] and some Chan-Kan, rarest yakus of all Mahjong except Yakuman-Agari, so enjoyment wise, I was satisfied enough
Overall: 8
To most of you who do not know what Mahjong is, this would be an Anime with some service-scenes and soft mahjong game with enjoyable plot. To few of who knows Japanese Mahjong, pure enjoyment and satisfaction, but some places you might feel discouraged to play more mahjong after seeing all those Rinshan-Agari
