Sweave for complex projects (speed issues)

One problem my colleagues and I face is that our statistical analysis projects quickly become very complex, and recompiling Sweave becomes a slow process each time I update the code or just run it again.

I am slowly compiling a list of available solutions to this problem (the real issues are lack of speed, lack of modularity):

Here is what I have found so far:

1. Use \SweaveInput for including modular code
2. Use makefiles a la Deepayan Sarkar:
here
3. Another solution that relates to the present problem:
here
4. Finally, I think one should make vignettes/packages out of one's research projects so that the whole Rnw file does not need to be compiled--the needed objects can be made visible by doing something like:

library(mydata)

There is a bit of work involved in making the package, but the payoff is tremendous. The R documentation provides details on how to build packages, but maybe I will put a simple example here.