I wrote the initial patch for the UUID support! It's my only Postgres contribution so far (except for docs), and I really only write C a few times a year. I made a few revisions but as I fell behind others picked it up and got it over the finish line. I'm pretty proud to say I participated, and maybe others can be encouraged to get involved too. Most of my day I write Ruby and Javascript. :-)
The issue with that is performance and index size. At first that was my solution, but as more data got into the tables that just wasn't working. For UUID's I had to move to casting to bytea using the uuid_send(uuid) function.
For enums, I had to create a function to cast an enum to a unique integer, and used that in my exclusion constraints. It's hacky as hell and not something I like, but it's worked for the past 3 years.
I'll be really really happy to get rid of those hacks come PG 10 though.
