Arrr, my insanity. Wolfgang is correct, of course.
Gee, and I was just going to ask why on earth you liked high-boot :)
I've seen one novel use of high-boot that could make it useful if you're lazy and can't be bothered plugging in your debugger ;)
Assuming your board has a toggle switch that sets the state of BMS in the RCW (as most Freescale boards do), you can put a 'good' version of U-Boot at say the high-boot location, and the test version at the low-boot. If the low-boot version doesn't boot, power-down, flip the BMS toggle switch, power-up and boot-high, reflash to the next low-boot test version, and continue.
I personally haven't tried the trick, but it sounded like a nice idea.
Low-boot is the only sane method for booting, since high-boot sticks the bootloader 8MB into your 32MB/64MB/etc Flash ... I mean who uses 8MB Flash these days ... :)
Cheers, Dave