I'm doing RaF now, and can confirm that rested xp doesn't get used at all while boosting. My paladins are 50 now, and still show +2500 bonus xp from the last time I used them at lvl 20 I think. And they went from 20-50 last night in an extremely casual night of boosting(afk half the time).

I dumped 4 accounts, which had 2 high level toons each, and started 4 new ones. Have an account with 4-5 80+ toons, and that became my booster account. $50 each for the upgrade to cata, so that's $200. I get 3 months to boost new teams, and each team takes something like 2-3 days of normal play time. At this rate I'll get have 5 accounts with all the classes on each well before RaF ends in 90 days. Free level grants cuts that time down some more. Maybe I'll get bored of it after a while, but that's the plan at least.

I had the same idea as you Jack, then asked for help in another thread. They recommended RaF and dumping the old accounts. Might seem like it's not worth it, but it is. Indeed.