I've had many PSR's almost slip out of my hands. Yamaha was really smart to make this keyboard so easy to grip. For a gigging musician, this is a major improvement.
I also like that the inputs are a little recessed making it less likely to have an accident.
A few years ago, I pulled my back, and my wife came with me to work to help me set up. She was in a hurry to get out, and packed my S970 before I removed my USB. At my next job, the USB drive had been pushed into the keyboard. I had no access to my USB drive, and I had saved no registrations to my USER drive, and the show sucked, and I lost a twice a year client. It cost $350 to fix the keyboard as the USB drive was integrated into a motherboard. This accident might be prevented with the design of the SX keyboards which has the inputs recessed from the bottom back of the keyboard.
Kudos to Yamaha.