This [REST/the Web] does not solve the general negotiation problem (which is probably unsolvable short of artificial intelligence) but brilliantly raises the integration watermark above which it becomes an issue, this significantly reduces the amount of custom coding you need to do to get a conversation going.
I can see benefits in the REST approach (ease of use, flexibility, simplicity, …). I fail to see this one, though. The amount of custom coding required is reduced compared to what? Compared to using plain sockets: yes. Compared to the much-hated, RPC-style, initial Web services approach: no.