I've been testing out a Lexar 133x 8GB CF, using the Dealextreme adapter, on my F20. No issues, assuming a recent bootloader and recent build. Slightly faster than using a HDD (since there's no spinup), and full screen 4:3 video isn't showing any dropouts. Adorama Camera had a recent free after rebate CF deal (I'm not kidding), so this was too good a deal to pass up. SSD's seem to be overkill, given the price.
I don't know if battery life is longer yet, but I would expect that it should be.