I'm an advanced amateur and have had the CMS-600 L for 6 months and played it almost daily. It is attractive and seems well made and I'm pleased with it, though I have three issues. 1) The low Bb key is a bit awkward, but I've adapted. 2) Initially, the low C, B and Bb were unstable; this disappeared after a month or so, maybe because the pads became seated, or maybe I became more familiar with the instrument. 3) With the included melody mouthpiece, or any alto mouthpiece, it plays extremely sharp. The neck isn't long enough to get it in tune and I have to pull the neck about one-half inch out of the body. There are still a few notes (middle D) that are difficult to play in tune.
I like the sound of the included "no name" mouthpiece and find it responsive and bright. I've tried various alto mouthpieces and like the Otto Link Tone Edge 5 star best, but not as well as the included mouthpiece. I also purchased a Caravan C-Tenor mouthpiece made for the C-melody sax that uses a tenor instead of alto reed. The Caravan has much better intonation and a very warm sound, that I personally do not like as well as the brighter sound from the alto mouthpieces.