Nick,
thanks for the link to your bootloader upgrade program. I have successfully upgraded few mega2560 bootloaders.
I have ProMini 5v 16MHz with ATmega328 chip. Stock bootloader has some problems with watchdog. (if wdt is activated board continuously reset, unless you make power cycle reset).
So i use Nick`s bootloader upgrade program and reprogram Pro Mini with Uno bootloader (i have only this option) The Pro Mini with Uno bootloader is working fine and fully support watchdog.
Can I expect some problem with ProMini with Uno bootloader?