At work I am part of a team that develops a process engine, so this BPEL resource center is of immediate interest to me. BPEL is promising, and also - having a solid theoretical base (PDF) - interesting.
It is however - and this seems to be a big-iron XML theme - gunky. Check out the sample scripts for examples of this. E.g. this representation of "output=4/2".
I'm all for metadata and machinable information, but there are costs. A painfully obvious one is that it will take a high level of tooling to make this healthy for programmers to consume and produce.