booting with keyboard open, I get the following options with booting results:

1. Maemo 5 (Internal Nand) = booting OK
2. Maemo 5 with 2.6.28-omap1-fb = booting OK
3. Maemo 5 with 2.6.28-omap1 = booting OK
4. Maemo 5 with kernel-power 2.6.28.10-power49,pre50 = reboots to U-boot menu
5. Maemo 5 with kernel-power 2.6.28.10-power49 = reboots to U-boot menu
6. U-Boot 2011.12.1 with zimage 2.6.28-omap1 = returns to U-boot menu
7. U-Boot 2011.12.1 = returns back to U-boot menu
8. U-boot console = opens console

Ah, one thing to note: The keyboard must be open before the power key is pressed. With multiboot, it was ok to press powerkey and immediately open keyboard. With U-Boot it doesn't work, keyboard shall be opened first.