I’ve upgraded a colleague’s K750i to the latest firmware: the much maligned R1DB001.
Had we been able to upgrade her phone earlier, we wouldn’t have been faced with the option of sticking with R1N035, an old firmware that still has the USB transfer bug, or upgrading to a new one with lowered volume levels, as reported in various forums by those who upgraded.
You see, Sony Ericsson’s firmware update service does not allow you to choose which firmware to install, it automatically installs the latest version for your country.
I’ve already decided not to upgrade to the latest firmware. My phone already has the latest prior version: R1CA021. The reason I’m not upgrading to R1DB001 is the universal complaint against its media player and sound quality, as can be gleaned from forum post after forum post in Sony Ericsson message boards.