Michael,
At this point, ampr-ripd (C implementation) is the best thing out there in my opinion.
Hessu, wrote the rip44d, and that required Perl and a multicast package to run. So running this on a WRT54G, for instance was probably not going to happen. I'd like to think with the C implementation, this could be a reality.
Also, I am not sure, but do think the C implementation stands the greatest chance to run cross platform. Hessu's perl one was kind of locked to Debian installs.
Again, it's all so new, I personally haven't had they time yet to try it on a bunch of different platforms.
I actaully am not sure why someone would go with amprd over ampr-ripd. Perhaps others can comment.
Steve