fixes and new features of the RapidInformer V1.2 build 371 ?

Yes, these issues/enhancements and several others have been included in this release. The list of fixed issues have been updated.

Items not in build 371:
- Simplified UI does not display the current user
- Route update bug fix (fields cannot be cleared during update)

Items in build 371:
- E-mail channel supports multiple SMTP servers
- New simplified UI allows users to define routes for multiple channels simply by selecting check boxes
- Filters are sorted by name (case sensitive)
- logout button is added to simplified UI and the config wizard
- Enhanced embedding command links into routed e-mail messages
- Groovy TemplateEngine memory leak is fixed.
- Notification reader TailMode functionality is added to admin UI.
- Members of the buddy list are recorded at the time of message delivery
- UI bug fixes (buddy list sorting, case insensitivity).
- Scripting framework autoerror handling mechanism
- Scripting API enhancements to make scripts more tolerant of exceptions
- Scripting performance improvements
- Sametime issue is fixed

Simplified UI documentation should be updated to reflect the changes in the build 371

The page http://www.ifountain.com/documentation/rapidinformer/accessing+rapidInfo...
is obsolete for the simplified UI part.
I would suggest to create at least a dedicated page for the simplified UI.

Diffs between build 371 and 373 ?

the configuration wizard is improved. It handles much more of the setup process.
The Smarts/Netcool modules include more commands.