Since MacHg 0.9.16 (or 0.9.15?) MacHg has its new push dialog (which is quite nice btw.). However, I've one suggestion:
When the user opens the Push dialog for a local repository for which he already did some pushing operations, the default item for "Destination" is the name of the directory (on the local file system) that contains the repository. I found this quite confusing (especially when the name of the directory is quite different from the repository's name) and it took me a while to figure out that this item represents the default remote repository.
So my suggestion is to add the repository's (bookmark) name to the item. So instead of reading "mytestfolder" it would then read "My Test Repos (mytestfolder)".
You may even consider dropping the directory name completely though I'm not sure whether there can be more than one item in the "Default Servers" group.