This is an impressive catalog of new features. Of course, the one that interests me most is the binary replication, but the ability to set schemawide and default permissions is going to be a huge boon as well.
I'm extremely dubious, on the other hand, of the utility of HStore. Not because I think the PostgreSQL implementation of key-value stores is faulty (I certainly would think not!), but because I'm dubious of the utility of simple key-value stores in a world where we have relational capability. But, if people are going to ask for it, I suppose there's nothing wrong with PostgreSQL providing it. Particularly since this way you don't have to choose between having two incompatible database systems, or sacrificing full relational capability, to have your simple key-value store.