I basically agree with Jenny, but since the OP wanted a list of pros/cons, here are some
advantage lattice: formula interface makes the code for lattice plots look a lot like the code used to create models with lm() and friends, simple plots are simpler to make and the code is terser, theming includes data elements and not just non-data elements
advantage ggplot2: better overall design that makes it easier to build up complex plots from modular elements, aesthetics for shape and size seem like a better idea than the "groups" idea of lattice, most people like the default look of ggplot2 plots better, now that it is relatively easy to create new stats and geoms I prefer to extend ggplot2 than to write panel and pre-panel functions for lattice
For quite a number of years, the advantages of lattice made it the package of choice for me when teaching beginners (using the mosaic package as well so that numerical summaries could also be done with same formula interface). At the same time, I did most of my own stuff in ggplot2, and when students outgrew the sweet spot of lattice, I helped them migrate to ggplot2.
Last summer Danny Kaplan and I introduced ggformula -- a formula interface to ggplot2 graphics. We created it with newbies in mind, but I'm finding that I now do almost all of my plotting with ggformula. I've heard the same from others who began using ggformula with students and migrated their own work to ggformula as well.
The biggest downside to ggformula is that it is the new kid on the block, and primarily provides a different interface to ggplot2, you don't get major new functionality -- just a different path to what ggplot2 can do. (To be fair, ggformula does add a few functions that make certain tasks easier to do than would be the case in ggplot2.)