Erik Malund said: in his post entitled the problem with
... JTAG is that you need to write a bootloader for on-site programming
Richard:
Why? I've never had to use a bootloader with JTAG. No JTAG programmable device I've ever used has required one. Bootloaders are use in place of more flexible hardware, I believe.
if you want your customer to do software updates, you do not want him to stick a JTAG adapter in and do it, thjat is where a bootloader comes in.

Keep in mind, please, that what I'm suggesting is that there be ONE and only ONE host-adapter, and ONE and only ONE device attachment allowing those same four signals, for all new field-programmable devices.
there will be a slight problem with the VERY small devices, you can not allocate 4 out of 8 pins for JTAG. Also just one pin (JTAG mode) could be a problem for these.

Erik

PS for my own purposes I really like JTAG, but have no intention of making that the option for field upgrades, I am currently developing "stick the USB stick in and wait for the message 'done' " for field upgrades