[R] Increased execution speed of R2.0.1?

[mkondrin@hppi.troitsk.ru]

Hello!
I have just upgraded from the R 1.9.1 to the latest version and
installed a couple of packages. I as a rule import only base package
with this couple of packages at startup. I was very impressed with the
speed R2.0.1 does now run (it seems to me I have 50% gain over 1.9.1
version). My question: is this due to "lazy-loading" mechanism (it looks
unlikely to me as IMHO lazy-loading conserves memory usage, not cpu
cycles) or are packages gots byte-compiled during installation (it is
more likely taking into account binary *.rdx files in R/library/...
tree). There used to be an alpha verision of byte-compiler for R - is it
now included into "official" version of R?
Thank you.