The SCX-56 (and presumably others in the SCX series) feels solid in the hand, and well build. It's a pleasure to play, the reeds are very responsive, and the mouth piece is very comfortable.
I've had to adapt my technique a bit to get the high B (hole 12, draw) and the low E and F (hole 3, blow/draw) to sound properly. From what I have read in many places, this is normal - new players should be aware of this, some notes require a bit of shaping your mouth to sound properly.
As chromatic players know, you need to pre-warm your harmonicas to avoid stuck valves. I have found this harmonica to take a bit longer to warm up than my other harmonica (Larry Alder Pro 12) - though as it's substantially bigger, that makes sense.
The slider can get stuck after some weeks of playing, and needs cleaning. My other harmonica has the same problem, so I'm used to it, though I'm told some chromatics are more prone to it than others. For this model I would definitely recommend putting some oil on the slide to avoid this happening too often. Suzuki actually sell oil for this, though I've used generic oil which works perfectly well.
Of the two chromatic harmonicas I've used, this is definitely the one I'd recommend ! As for the question of going for 56 vs 64, I went for 56 as from what I see that covers most music I'm likely to play, without the added bulkiness of two more holes I'd only use rarely.