Just quickly I think it's relevant to say that I'm a huge fan of the Bleach manga and a moderate fan of the TV series (except the filler sagas). This review assumes that people are familiar with the Bleach manga and/ or TV series. I would advise against watching this movie if you're not.
You know the great thing about making a movie follow up to a TV series or movie that is already popular? You can put in a fairly minimal amount of effort and still be guaranteed to make at least a decent amount of money, so long as you've conducted enough market research to give the fans of the original what they want. I watched the TV series until half way through the bount saga, then stopped and started reading the manga because the series had become slow moving and unimaginative. I subsequently found out that the bount saga wasn't part of the manga (a "filler" saga) and was made to make money rather than for the sake of art. Memories of Nobody is basically the same thing; a 90 minute filler episode.
Memories of Nobody is not a complete waste of space though. The voice acting (in the English dubbed version which I'm reviewing) is quite frankly excellent. The plot - while inferior to Tite Kubo's masterpiece - is better than what you'd get from a lot of action movies and fits with the tone of the TV series without clashing with it.
And what about the characters? Joining Ichigo and Rukia is a third main character - a mysterious young girl named Senna. (Mysterious young girls in anime?!? No way!!)
Senna is a hyperactive demi-loli who runs around giggling and annoying Ichigo. She is given a sob story background to try to force an emotional attachment from the viewers, but unfortunately that's about as far as the character development goes and so she's very one dimensional. This means the character really isn't believable, which means we don't get the emotional attachment, which means we fail to care.
Ouch.
All the most popular characters from the series make appearances which should make the fans happy, but they haven't gone to the effort of properly integrating them into the main story and so they just end up feeling like cameo appearances (you're guaranteed to make money so long as you give the fans what they want, remember?)
The movie could have (should have) built upon the series by riding it's strengths while providing better quality animation and getting rid of the super-cheesy music, but the animation quality hasn't noticeably improved and they've kept the same cheesy music from the series. It has its good points and bad points, but all the bad points easily outweigh the good ones. For example: It's a Bleach movie! YAY! The animation is TV series quality! BOO! It's got Kenpachi in it! YAY! The main character is about as deep as a puddle! BOO! Etc.
Basically Memories of Nobody only ever aspired to provide a pleasant experience for the existing Bleach fans and because of this it was never going to be a great movie in it's own right. Even for fans of the show this is definitely "rent before you buy" material.