It seems the best information about the 37E, written some years ago, has come from this forum’s own Alan Brinton (hi Alan!), whose own review of the P-32D led me to buy one.
Sticky keys, also observable on my P-32D, seem to resolve themselves as one begins to play. It may be that Yamaha’s melodicas have this trait along with a bit of key noise, but I find it low enough not to be heard while playing.
I’ve not found a P-37E in local music stores, so maybe it’s not been the success Yamaha hoped for? The salesman, who’s known me for a long time (I’m a sax player), said the 37D is their top seller.
Alan’s review of the 37D makes me want one – and it has so much youtube exposure – but I honestly don’t think I can use those five higher keys. Perhaps, like the Hohner Marine Band harmonica, the 37D has become such a classic that every melodica enthusiast should own one.