Seems to me that posting here rather than on https://stat.ethz.ch/mailman/listinfo/r-help will give you replies that would be slightly biased towards ggplot2... 
To add on what @baptiste wrote about lattice advantages, I often finds myself frustrated with ggplot2 when it comes to fine control of my plots (especially in comparison to lattice with using custom panel and prepanel functions) and with how ggplot2 handles data panelling and grouping (ie, application of colors/symbol/line type within a plot or application of data transformation or processing by group).
People in my field tend to generate 1000s of plots during the development of their models. Speed of plot creation and capabilities to split the data more efficiently in lattice give it a slight edge over ggplot2 in my opinion.
That being said, ggplot2 is easier to learn and to apply in 90% of the cases...