Really the difference between a Rev A and Rev B are really minor. You could consider it akin to a 2005 model car and a 2006 model car (or a 2005 model stereo receiver and a 2006 model stereo receiver). The car dealers (and hi-fi retailers) don't offer an upgrade path for free either other than selling you a new car (or stereo).
Unless you are a constant CF card user, if you can get your hands on a 128MB to 256MB CF card and just leave it in the slot you'll be just fine (other than having to restart it each time you reboot). I run music and stuff all the time and often forget to engage the swap and things almost always work flowlessly except sometimes when using Mplay.
Also, I have used my Rev A remote from more than 30' away. I think the assumed lack of power seems to have more to do with direction the remote is pointed rather than it's power. My wife often holds the remote in her hand with it pointing ever so slightly upwards and then can't get the remote to work. I'll then grab it from her
and point the transmitter part of the remote at the Roku and it always works without a hitch. At least as long as the unit itself is not having lockup issues.
Maybe I'm just lucky????