Ouran is a very well done anime and while there is no actual plot (its more just a days in the life of type) the randomosity works extremely well for this show especially in the development of the characters and the intercharacter relationships.
Character development is amazing you genuinely get to know each character on a 3D level. From the cool (and sometimes devious) Kyouya to the calm, laid back Haruhi, to the bipolar Tamaki every character has some deeper fuller level of development and is more than just their surface type.
The animation is just extremely well done, the artwork is beautiful transitions are smooth and nearly flawless.
Now for the sound, I've seen this both in Japanese and in the English dub, honestly I prefer the Japanese voice acting but the English one is decent. The Japanese voice acting is just closer to matching the character's personality than the English but both are still very good and the background music and sound effects are amazing.
Overall this anime gets a 9.5 because I really would have liked to see more done with the characters built up so beautifully and the ending was rather half-assed other than that this is a great anime and WELL worth watching.