Cool, WT and succinct data structures are definitely an interesting field these days.

I'm primarily using as a compact order preserving structure to support fast lookups for both (token -> position) and (position -> token). I'm using an updatable variant to support O(1) appends, and then use it for realtime indexing/compression. I probably should do a blog post at one point...

Would be interesting to hear about faster ways to do rank/select without using support structures... I'll keep an eye on your blog :-)