Ocean's 12 tried to be better than it's predecessor - and it failed, miserably.
The "Ocean" films (original and remakes) are based on the feeling of suave and cool that emanates from the characters. They're always one step ahead. You want to be them. The first film managed to achieve this suave atmosphere that the original had. The second however, destroyed it completely through bad cinematography, style choices, graphics and sfx. Apart from that, the script was full of self-referentialism and felt like an inside joke that the audience was doomed to never get.
The film is full of famous stars, and none of them get enough screentime. One is stuck in a jail for at least 2/3 of the film. This problem becomes evident in the "Julia Roberts" storyline which gives the audience the feeling that half way through the script - writers realised that they hadn't done anything with Julia since the 1st 5 minutes.
Alas, that story line is not the only symptom of the badly written script. In the last 5 minutes the writers realised they had made their guys look like dumb idiots - their solution? Add in a crazy backstory that the audience knew nothing about to explain how the guys got the Faberge egg without anyone (including the audience) knowing. (There weren't even any clues that the audience could look back at and say, "Oh, I see it now").
The badly written dialogue and script also resulted in some cringe moments, the destruction of the Italian language and some completely implausible "egg replacement" technology.
The film also has so many plot holes (mainly arising out of the "in the last 5 minutes backstory") that you could build a highway through them.
The "heist" film lacks any intrigue, logic or tension.
The other major problem with the film is the indecision and poorly planned style and cinemematography. Any film trying to re-package the coolness of Frank Sinatra and Dean Martin should not use hand held cameras, poorly planned angles and lighting, mismatched sound, and clashing stylistic elements. Nothing stayed solid from a technical angle of this film.
In fact the only good section of this film was in the first 5 minutes - the flashback to Brad Pitt and Catherine Zeta Jones past relationship. He stayed one step ahead and was very suave - but still seemed fallible, therefore the audience could relate to him while still idolising him. If the film had continued along this path - I wouldn't have felt like I'd been robbed of my time, money, and brain matter.