Same here, I think G needs at least 1 year to handle your site “serious”. On SEO forums there is a theory that it could be lasted now 2 years (considering that the top sites in the serps are more than 2 years old.) PR has nothing to do with position, some of the top sites in G have very low (2-3) PR.
For some weeks now I got some visitors from G (about 3-4 daily), but not from the general search page but the picture search.
Maybe it will climb up with time 