We're going to use SSNS 2005 to build an uber-notification system for our application.
The idea is that we'll ship with some "hard coded" notification types soon, and in the future build more notification and a cool way for users to add their own notifications.
I was unsure whether all this would be achievable in SSNS, but after a few weeks learning and mulling over how we should use it, I'm quite happy now that its going to do exactly what we need and then some :)
SSNS 2005 has a few new features that make it very flexible - it can be hosted in your applications database, which means if you need to pull data out of your own tables for generating notifications, then its so much easier. I think the flexibility is its strongest point. You can get it to send notifications for pretty much anything, and if you need it to do something wacky (like notify to a fax machine!), then its really easy to build your own notification components using .NET.
I'll be posting more on this soon - I'm planning on posting some code just as soon as I get something mildly interesting to show :)