I finally found some time the last days to play with my new PandaBoard ES. As first Dirk Müller helped me by providing an image for my SD-card with an image that worked with the normal PandaBord. Thanks! Unfortunately we couldn't get the machine running with this image.
Later I tried a Linaro Android build and the machine booted. As I copied some of the files from the boot partition to the SD-card with the openSUSE installation it booted into openSUSE. After a hint from Alexander Graf (to change the console in u-boot to ttyO2) I could also access the serial console.
I could now play around and build on the board to find a fix for the openSUSE image Dirk provided to me: Since it didn't boot with the latest u-boot/x-loader git code from mainline, I tired the u-boot git from Linaro. This step finally solved the issue. I created a new u-boot package for openSUSE: u-boot-linaro-omap4panda. While the upstream u-boot package deletes the MLO file at the end of make, the Linaro u-boot doesn't. Therefore the new RPM should obsolete x-loader-omap4panda at openSUSE.
You can get the Factory RPM (temporary) here. I already made a submit request for Base:System ... we will see if and when it gets in.