I can't say I have a love hate relationship with what I'm currently using, which is a PSR-S910.
My only complaint about the previous model, the PSR-S900 was the organs didn't sound like Hammonds...they were okay, but there was room for improvement.
This S910 has better organ sounds...much better, SA better. Jazz Rotary and Rock Rotary are wonderfully Hammond-like, and are inspiring to play. I find I play the licks I used to play on my old Hammond...I didn't get that feeling with the S900.
Improvements? Nope, I'm pretty happy with this one. I like it more than the Tyros3, so that's saying something.
Only keyboard I had a bad relationship with was a Roland KR-650, which I bought to replace a Roland E-70.
The keybed was like the ones in the EP Pianos, and the keys were shorter, and the OS wasn't all that pleasant to work with. The piano was awful, especially in the mid-range where you play most often. It got to where I didn't look forward to gigging, so it was time for a change.
I got rid of it and got a PSR-510. Been using Yamaha ever since.
Ian
_________________________
Yamaha Tyros4, Yamaha MS-60S Powered Monitors(2), Yamaha CS-01, Yamaha TQ-5, Yamaha PSR-S775.