Nifty...

I assume that only characters of a particular faction can trade heirlooms to characters within said faction. Would they have to be on the same server too?

Ahpffsh... I'll actually need to figure out which heirlooms I'd need for the toons I'd want to level quickly. Do they really expedite the leveling process to, say, being able to get a toon to 90/100 in a few hours? A few days? Is this heirloom dependant?