So, here are my results using USB Host Mode beta release so far.

Sandisk Cruzer Blade 4Gb flash stick worked perfectly via high speed mode. I was able to watch videos from it using the Media Player, and copy files to the 32Gb internal storage as well as the 8Gb MicroSD card I have, and back to the flash drive again. no playback issues at all, and no write protect issues.

250Gb external powered HDD did not work, however this HDD only works intermittently anyway. Nothing to do with H-E-N IMO.

500Gb external passport HDD, which is supplied with a dual USB cable (second plug provides additional power). This did not work. We powered the second plug via a USB power supply, but no luck. I forgot to check the kernel messages.

HTC Desire worked, and started charging! It read the 32Gb MicroSD inserted, and successfully played some music with no issues (although Media Player tried to retrieve all the "new" media's information).