I'm with Scott, Steve and Jazzhooves, although I haven't got a Tyros4 yet, I have a Tyros3, and have used Tyros2 and Tyros extensively.

Some people like Yamaha's OS better than the others...some don't...no big deal...buy what suits you.

I'm enjoying a PSR-S910 at 1/3 the cost of a Tyros, and it's OS is excellent for "live" performance.

To each his own...