Yeah, I remember when we did an AUKN top 5 manga thing, and the Beck manga did really quite well, only being beaten by Fruits Basket (about 5 times over, but still...).
To be fair, there are lots of reasons that someone could be put off watching Beck; the character designs, the engrish, the slow-moving story, not liking the music...
Even so, I consider it fairly highly just because it tells such a good coming of age story - not as good as FLCL does, perhaps, but I can't think of any others that do this better.