In terms of the number of listings you can import, there are limits relating to Geocode data as mentioned on the actual
importer page, with more information also available via
this blog post. You can import listings with attachments and all of the listing information you'd see in Vantage using the default example file, but you can also customize the importer
as outlined here. And as of
Vantage v1.2 which is due for release soon, there will be Rich snippet microdata for
SEO (assuming that's what you were referring to with the ratings appearing in Google? if not, please feel free to clarify what you mean). Thanks.