Today marks the official release of Apache.NMS.ActiveMQ v1.5.1. We put a lot of work into this one fixing bugs that were found since the 1.5.0 release. The MS Distributed Transaction Support should be much more stable in this release.
For anyone on v1.5.0 I'd definitely recommend upgrading, there were a couple of threading issues that have been resolved which should make things more stable.
The v1.5.1 release page is here