1. Seems like preview listening in Finder is adiquate. But, if it could also read the Serato library that would be helpful because that's really the issue - Finder is lame compared to Serato's Library. But maybe that's tough to build in.
2. Personally, I'm using like five to nine sample a time it's fine for me. But I think it should have a keyboard set up. I'm usually using MPC with 16 pads, but sometimes I'm using a keyboard and knowing which sample goes to which key is annoying, maybe in that case 2 octives of keys?