A bootloader can be handy mechanism for updating programs on products in the field without a programmer but I find them handy for development work as well...
On the 16F' devices with self-programming capability you can program code/program memory and eeprom memory...
On the 18F' devices with self-programming capability you can program code/program, eeprom, IDLoc, and config' memory, though many 18F' bootloaders disable config' memory modification for obvious reasons...
If you can spare approximately 100h words on a 16F' device or 200h words on an 18F' device, a bootloader might be a viable addition to one or more of your projects...
Microchip application note AN851 provides sample bootloader firmware for 16F877 and 18F252/452 devices as well as the PC side software... Caveat -- I seem to recall their PC side software may be a little buggy...
Regards, Mike