I discovered the same issue and it took about an hour, maybe two, before it felt normal. I also struggled with the scrolling for about as long. Since there is only one button I don't see any other way for the mouse to know to pay attention to a sensor on the right over a sensor on the left when both are activated unless you can measure and meter the pressure through the plastic skin.
It's certainly a limitation, but one I will live with as I'm pretty tired of cleaning the ball on the Mighty Mouse. I've been cleaning the balls and spoke wheel sensors on mice since my IIci, this includes Kensington Turbo Trackballs, Logitech mouse-of-the-month, and many other brands of mice. The mouse I'm using right now will scroll down, but not up. It seems like the time between cleanings is getting shorter all the time.
Since it doesn't cause a physical problem for me to lift my left finger while pressing down with by right finger, I will gladly switch to a mouse that will work for years without having to worry that dust, cat hair, finger oil, etc will eventually cause tracking issues. It's my biggest complaint for the Mighty mouse and I've had several clients call me to get a new Mighty Mouse because they believe theirs is broken.
I turned on a hot corner to replace the button I'd set for Dashboard and I never used the side buttons for Exposé.
Not a perfect device, but I'm going to be getting them for several machines. Meanwhile, I will trade any of my clients a Mighty Mouse for a Magic Mouse, and even offer a few bucks or discount a repair. 🙂