I haven’t been using Posterous as much as I would like, but I’m keeping an eye on what they’re up to. Today Posterous added theming, allowing users to more creatively style the look and feel of their Posterous sites.
I don’t know how well it actually works, but from reading the description Posterous was smart in the theming mechanisms it made available. First, you can just pick from a canned set of Posterous provided themes. Second, their engine is compatible with themes for Tumblr. This taps into a vibrant, pre-existing market or power users can write their own themes.
They’re quietly flying under the radar, but I get the sense that the Posterous team is putting together a good product.