I just finished watching episodes 1-3.
Magical Angel Creamy Mami is an old series--it dates back to 1983, and there are few anime series available anywhere which are this old. The few exceptions include Astro Boy (Tetsuwan Atom), Gigantor (Giant Robo), Star Blazers (Uchuu Senkan Yamato) and others.
Urusei Yatsura is of about the same vintage, and it shows in the art style. Besides that--as I recall!--it was produced by Studio Pierrot, the same company which produced Creamy Mami (and other series).
The most interesting thing that struck me about Creamy Mami, right off the bat, was its similarity to Magical Stage Fancy Lala, which was released as simply Fancy Lala here in the US. The basic plots of both series start with a young girl, around 8 or 10 years old, who is given an object which bestows magical powers on her, and the primary manifestation of this magical power is to make her appear to be about 15 or 16. In both series, the main character then suddenly finds herself becoming an idol singer.
Fancy Lala is also a Studio Pierrot production, and it is fifteen years newer than Creamy Mami (it came out in 1998) so--having seen only the first three episodes of Creamy Mami--I have to say that Fancy Lala almost looks like a derivative series, if not an outright copy--even to the fact that the main characters of both series have a pair of cute mascots. (Mami has two alien kittens, a male and female, who talk and advise her. Lala has a pair of baby dinosaurs, a male and female, who talk and advise her.)
The art and writing of Creamy Mami come from a time when the animation industry in Japan was just finding its artistic legs. The production values are not very high compared to modern productions; perspective and proportioning sometimes suffer. The series is clearly aimed at a young audience, and it seems not to have much to attract the attention of the adult viewer, unless the viewer in question is already a big fan of magical girl anime.
Having seen three episodes, though, I can say that the series is entertaining, and once one makes allowances for the production values, it's worth watching. Then again, I really enjoyed Fancy Lala, a series which has left other anime fans cold. Other people have said that Creamy Mami is a prototypical magical girl series. So determining the overall value of the series is probably best done by watching an episode or three.
As for my opinion: Creamy Mami, as of the third episode: 3 out of 5.
IMDB entries for Creamy Mami:
and Fancy Lala: