There's so many emotions inside me about this manga that I'm having a really hard time finding words that express them. I settled on "masterpiece" after a lengthy internal debate about what adjective to use. Was originally going with "magnificent", but Beck's greatness is subtle.
They have awesome parodies of famous album covers, I recognized Coldplay's Parachutes too.
To me, its biggest strength is the pacing, which is perfect. The biggest compliment I can give is that Beck's pacing is as great as Honey & Clovers. Koyuki can totally be Takemodo and Ryuusuke can totally be Morita...well the parallel ends there haha.
There's a balance of the highs and lows, but with just the right amount of pauses so that you're not overwhelmed and can appreciate the growth of the characters. The story spans 6? years, which is a realistic time frame for a tremendous amount of character development, heck you can even see the appearance of each character growing up. My only two complaints are 1) that Izumi never re-appeared, since she played such an important role int he beginning; and 2) the rivalry with Eiji didn't receive a proper conclusion.
Beck also has a strong set of characters, including all the supporting characters. The struggles and set-backs that each character experiences is also realistic and easy to relate to, which is another similarity with H&C. Beck does such a good job of drawing you into their world, I feel left in such a daze now that it's back to real life. No worries, going to watch the live-action movie after making this post.
The soundtrack (for the anime, and a tribute album) is great as well. You really ought to listen to them as you read the manga. It may seem odd to read the manga about music instead of watching the anime where you can actually hear the sounds, but I feel strongly that there are a couple scenes, especially between Koyuki and Maho, that work much better in panels of image. Also I read the Japanese voice actors pronounced the English lines pretty badly, but for the soundtrack, that adds character haha. I'm saving my favourite songs to post later as filler material for when I start working, but Moon On The Water occupies the same space in my heart as Goodnight Julia from Bepop.
Needless to say, from my comparisons to H&C and Bebop (honestly the highest praise I can give), that is my favourite manga. Heck I don't even remember what my previous favourite was (probably Ares, which I also love dearly and is severely underrated!!!). Oh this also very similar in subject matter and premise as Solanin, again severely underrated and you should definitely watch.