Dear Andrew I use RadControls for this.
Here is what I have.
Tamplate Home with main navigation
Tamplate Normal with subnavi in it
I use RadControls for Subnavi (you need to acitve them in Admin - Advanced - Toolboxes - Radcontrols if I remember correct)
Then under Daten Drag the Sitemap Datasource to your page (sorry SBE German no way to know what's it in english) sf_subnavi_01.png
ShowStartingNode = False
SiteMapProvider = SitefinitySiteMap
StartFromCurrentNode = False
StartingNodeOffeste = 1
Copy the ID to clipboard Ctrl + C
Then drag the RadControl (I use Panelbars a lot) to the template page
DataSourceID set to the one from sitemap datasource Ctrl + V should do the trick.
Remember for styling you need to turn off embeded skins and stuff.
Old fashion, not out of the box, but works every time and I can set my own styles which is less then using embed.