great graph overlay/transpose -- i've found posterous to be much faster in my infrequent use of both tumblr and posterous -- also, i'm not a fan of the commenting mechanism (reblogging) from tumblr -- for folks who use it often, they love it, but i find it to be really nonintuitive. makes me think that the early adopter's love it, but to go mainstream they'll need to shift it, which will turn off the early folks. posterous, by comparison, just does things fast/elegant, which seems more broadly appealing. time will tell.
Yeah, I find reblogging and some of the other mechanisms in Tumblr to be kinda jumbled and confusing. On pure merit, I tend to lean towards Posterous... If I were more of an early stage investor, I think I'd want stock in BOTH. :-)
