Well, I've just completed a mod of my H140 using the following CF card (Kingston Elite Pro 32Gb):
http://www.buy.com/retail/product.asp?sku=210728700&listingid=39938766&dcaid=17902In a nutshell, I carried out the following steps:
1) Installed Rockbox 3.2 on my H140 hard drive (previously having version 3.1 installed, along with bootloader 6).
2) Followed the instructions here to get bootloader 7pre4 installed:
http://www.rockbox.org/twiki/bin/view/Main/IriverFlashing.
NOTE: It is important to carry out the sections on flashing ROM and RAM in addition to adding the flashing the new boot loader. Doing so deletes the original iRiver firmware, but it is a necessary step in order to get the above card working, otherwise all you'll see is an ATA error: -80.
3) Followed the Bootloader configuration steps from the link above and selected to boot from ROM. Set this to the default.
4) Installed rockbox 3.2 on the CF card, copied over my music from the drive to this disk and installed the CF card inside the unit (with the required adapter).
5) Switch on the iRiver and watch that baby fly ! It's lighter, faster and absolutely silent !
The USB mode bug (ATA error -80) is still a problem but I was able to simply switch the unit off and back on again. I didn't need to reset the unit.
Of course, I'm not claiming any responsibility in the event you brick your unit, but I hope this helps with your decision to give it a go.
Mike.