As the author of a crash reporting framework, this is the first time I've seen execution speed of a frame unwinder so strongly touted :-)
Without code, I can't make much of a comment otherwise, although I'm certainly interested to see your patches to libunwind once it's upstreamed.
One of the reasons we didn't use libunwind in PLCrashReporter (and instead, wrote our own DWARF unwinding code) was the relative difficulty we saw in porting libunwind to Mach-O and the Mach thread/VM APIs, as compared to the cost in porting our relatively platform-neutral code to other platforms.
The analysis side is super interesting too, and it'll be great to see more of what emerges from your work. I can't think of much that's been published on that front other than Microsoft's overview of their Windows Error Reporting heuristics:
http://www.sigops.org/sosp/sosp09/papers/glerum-sosp09.pdf