The only bootloader I've played with is Tiny (http://www.etc.ugal.ro/cchiculita/so...bootloader.htm It worked with an 18F2550 and as far as I know claims to work with most 18F chips...

Unless you are making a product that needs updated firmware in the field, or a device that uses PC software and could pull down any firmware updates then I can't see the advantages of using a bootloader over ICSP or programming on a development board