Securing Messenger 6.1 (Hardening)

I'm looking for admins or end users who have experimented with securing the Messenger IM client.

We're an all-MS shop (I know, I know...) and Messenger will serve as a mobile communications tool (IM, SMS, voice and video, whiteboarding, etc.). The data passing through it could be considered highly confidential at times and needs to be encrypted.

I've looked at a few products (Secway's Simp and NetIQ's imMarshal are on my list already) and I need real opinions and appreciations. If the solution is centrally managed, that would be even better.

If you've deployed a corporate solution to secure IM, or if you've experimented with it personally, please post your comments and/or recommendations.

Thanks!