I can't answer your question -- however, given the reports following the first BCD536HP firmware update (1.03.03) suggesting the radio (for some) didn't work as well as before the update, I wouldn't rush to do any update until hearing reports from others. I blindly updated my 536 and I know at least one feature didn't work the same/as well after the update.
Additionally, I recently acquired a "loaner" BCD436HP (with the latest firmware 1.03.00 installed) and in many ways, I think it is functioning much better (scanning faster, receiving more activity, receives/better processes digital voice on Motorola Type II systems, etc) than my BCD536HP. I've only had the 436 for about 2 days and need more time for a more complete comparison.