Learning ggplot2: 2D plot with histograms for each dimension

Update (April 2013): The code below doesn't work anymore with new ggplot2 versions, here is an updated version.

I have two 2D distributions and want to show on a 2D plot how they are related, but I also want to show the histograms (actually, density plots in this case) for each dimension. Thanks to ggplot2 and a Learning R post, I have sort of managed to do what I want to have:

There are still two problems: The overlapping labels for the bottom-right density axis, and a tiny bit of misalignment between the left side of the graphs on the left. I think that the dot in the labels for the density pushes the plot a tiny bit to the right compared with the 2D plot. Any ideas?

Here's the code (strongly based on the afore-linked post on Learning R):

p <- colour="cyl)<br" data="mtcars," geom="point" hp="" mpg="" qplot="">
p1 <- br="" legend.position="none" opts="" p="">
p2 <- aes="" colour="cyl))<br" ggplot="" group="cyl," mtcars="" x="mpg,">p2 <- br="" fill="NA," p2="" position="dodge" stat_density="">p2 <- axis.title.x="theme_blank()," br="" legend.position="none" opts="" p2="">      axis.text.x=theme_blank())

p3 <- aes="" colour="cyl))<br" ggplot="" group="cyl," mtcars="" x="hp,">p3 <- br="" coord_flip="" fill="NA," p3="" position="dodge" stat_density="">p3 <- axis.title.y="theme_blank()," br="" legend.position="none" opts="" p3="">      axis.text.y=theme_blank())

legend <- br="" keep="legend_box" opts="" p="">
## Plot Layout Setup
Layout <- grid.layout="" ncol="2,<br" nrow="2,">   widths = unit (c(2,1), c("null", "null")),
   heights = unit (c(1,2), c("null", "null")) 
)
vplayout <- br="" function=""> grid.newpage()
 pushViewport(viewport(layout= Layout))
}
subplot <- function="" layout.pos.col="y)<br" layout.pos.row="x," viewport="" x="" y="">
# Plotting
vplayout()
print(p1, vp=subplot(2,1))
print(p2, vp=subplot(1,1))
print(p3, vp=subplot(2,2))
print(legend, vp=subplot(1,2))