I spend couple of hours yesterday playing with "Any transport over MPLS" and it works. It's easy to configure and easy to troubleshoot,anyway, I am not writing this post because it's easy to configure some MPLS application but because I tried it first on cisco 3725 and I hit some issues - so my advice is - if you are using dynamips and want to try some MPLS features just don't do it on 37xx platforms, use 72xx.