I've configured my device (a Seagate DockStar) with just two NAND flash partitions -- one for u-boot and one for the Linux rootfs.
This has some nice advantages: it maximizes the available flash space, and allows the Linux distribution's own tools to install new kernel and initramfs files without having to know about flash partitions.
But I just discovered that it has a fatal disadvantage. My device can't reboot when the ubifs is corrupted, which happened today after a power failure:
UBIFS: recovery needed Error reading superblock on volume 'ubi:root'!
Ubifs includes recovery code, but since u-boot treats it as a read-only mount, this is never performed. Once I booted Linux, everything was fine.
I'd like to request that the read-only flag be removed (at least to allow recovery) so that the ubifs-only scheme can be used reliably.