As stated under WARNING at http://blog.iphone-dev.org/, ultrasn0w will soon be updated to be compatible with FW 4.3.1. This updated ultrasn0w can then be used on the older basebands. But, which older basebands? Is it going to be only for Baseband 01.59.00? Or, is it going to be for Basebands 01.59.00 and 02.10.04? When I purchased my iPhone 4 in August 2010, it came with Baseband 02.10.04. That's what it says under Settings General > About > Modem Firmware.