I used to read on my Palm--it was backlit. Don't know how it compares to the REB backlighting though. I noticed a lot more eyestrain when reading on my palm as opposed to reading on my PRS505. Even though it's a bit of a pain, I much prefer using a booklight in bed with my Sony as opposed to back lighting.
I agree with Bob as well--since the formats are not compatible, it would be quite a pain to try and pick up where you left off on your other device. I'll stick with my $5 booklight
dordale