ok the webpartactions are now working for me!
maybe i overread the part or its not so well mentioned in the readme - anyway, here are the steps i did additionally:
check the folder "MySiteCreatePart" that comes along with the mysitecreate-feature.
1. Open the stuff.txt and copy the "Master Page Registration Tag" and the "Master Page Tag" in your masterpage source code.
2. I copied the Master Page Registration Tag just beneath the last "<%@ Register Tagprefix ..." on line 6.
3. I put the Master Page Tag underneath the <WebPartPages:SPWebPartManager id="m" runat="Server" />-control in the <form>-Tag.
4. save your masterpage and use it as described in the readme.
5. now you just need to register the mysitecreatepart.dll via gacutil. you can use the code from regpart.bat (inside the mysitecreatepart-folder).
now your ready. hope it helps someone a bit ...