It would be great to use the site name in page title if I choose it in the global settings.
Here is a hack solution: http://forum.virtuemart.net/index.php?topic=108776.msg371876#msg371876
The other similar question is the meta description autopopulate whit this hack:
https://forum.virtuemart.net/index.php?topic=102251.msg361649#msg361649
It would be great to implement these features into the base component
you don't need a core hack, you can achieve this also with template overrides
http://docs.virtuemart.net/tutorials/33-templating-layouts/78-introduction-template-system.html