This would have been perfect around a year ago. Once the writing was on the wall, I migrated 4 or 5 sites (kinda, mostly) to self hosted Wordpress. I would have happily shelled out $5/mth to go to posthaven, had it existed.
Because WP bugs me, I've written my own lightweight markdown based thing in node[1] that I'm gradually moving everything to.
On the upside, the Posterous thing finally taught me to not rely fully on free services, no matter how good the feature set.