I wouldn't right off the toro just yet. It sounds like there is a repairable issue. In the back of my mind, i wish toro had come out with the GS sooner, i might have bought it instead. Seems like the grass is always greener on the other side.
Can you look at your machine when it's not running and verify that the linkage on the side of your pumps is moving equal amounts on the right and on the left? If it is, you might have a pump problem and a pressure test might show it up.
I know how it is when you know there is a problem but the dealer says its fine. It is extremely frustrating. Warranties have limited value.
How many hours are on your machine? What size and HP? I have read your threads but cannot recall what you have.