Aside from just reporting the fact, I decided to write a short guided tour to get you started - and tested it with the most recent version of Windows Vista 5472.

1. Download from http://mwconn.tribal-sunrise.com/ - the site is still German-only, but simply click the link "Version 1.0".
2. Copy to folder UMTS
   
3. Right-click and Run as Administrator
4. You are asked for your preferred language - click No for English
   
5. MWConn asks to create connection-type specific program copies - choose Yes:
   
6. MWConn needs a connection to dial - it can create one itself, so choose Yes:
   
7. You will be presented a message box that informs you about connection creation success / failure. You are almost done, and your UMTS folder now looks like this:
   
8. Run UMTSGPRS (as Administrator). If asked again for the language, choose No to retain English. It will exit with a note that you should edit MWConn.ini.
9. Edit MWConn.ini - you only need to edit a few entries:
   
   08 COM=
   09 PIN=
   10 NET=
   11 APN=
10. Once done, start UMTSGPRS again, and you will be logged into your network:
    

For details on configuring the settings in #9, see the Comments section of my previous blog post Merlin - Yes, Magic IS Required.