> It's more than that. Many board vendors will use a secured stage 1
> bootloader that assumes U-Boot. It's probably possible to shove in a

good point.  what are the secure loaders assuming?

> Every SoC is going to have a different process - in the end, you'll have
> something that will probably look quite a bit like U-Boot without any real
> benefit. I'd rather tilt at other windmills...

that was my opinion, and i argued it pretty loudly—
until u-boot didn't cover my needs and i had to fix
u-boot.  i had to eat my words. 

u-boot is really terrible to work with.  there is no
danger of writing something that looks like u-boot.  :-)
but if u-boot works out of the box, i would totally agree,
why not use it?  but don't fall for the trap of modifying
it.  that's a terrible waste.  instead of learning about the
internals of u-boot, you could spend time learning how
the hardware in hand is really set up.