Good question Daren, There are a couple, weight would be the big one. If you play in a downward position it is not bad, but if you play in a trumpet position you will start to feel the weight quickly. Compared to the Piano-36 its a tank. If you own the version with the moisture release button, you can’t get all of the moisture out (it has a filter at the hole). The version with the screw cap like Bruno’s is much better, remove the cap and blow hard and a good amount of moisture will come out. The button is faster but not as effective as the screw cap version. I like to unscrew the cap, place the melodica on its stand put a towel under it and let the moisture fall out by gravity at the end of practice. The Solist has the button too of which I do not like so I tend to clear often. I have compared (2) pro-36 with the Solist and the Solist is by far louder than the Pro-36. I have one Pro-36 with no issues at all, no leaks nada almost perfect, and one with a very tiny leak at a key pad, the volume is at least 10-15% lower between the (2) Pro-36, so a larger leak can rally cause issues. And as you noted earlier on another post it is a complicated melodica to work on. I think the easiest melodica with single reeds to work on is the Clavietta.