[ESS] ESS on Mac slower than R.app?

[baptiste auguie]

Dear list,

I'm using R on Mac OS 10.5, with either R.app or ESS running with
aquamacs. The only reason I keep R.app is because I find ESS very slow
to run a given chunk of code -- copying and pasting into R.app is
often faster. I'm guessing that it's not due to ESS itself being
slower, but that there is something wrong with my setup.

Say I am editing a script that is 50 lines long. I start an R process
first, then hit C-c-C-b to evaluate the buffer content. I have to wait
almost 10 seconds before aquamacs responds again, during which time I
have the message "Starting evaluation..." at the bottom. If I copy
this code and paste it into R.app, the evaluation is instantaneous for
this particular piece of code (I don't know how to make a precise
timing but it seems less than a second).

I also tried C-c-M-b ("eval and go") and C-c C-r but the results are similar.

Needless to say, I am a complete novice with emacs. I'll appreciate any tips.

Best regards,

baptiste

ESS version 5.3.6

sessionInfo()
R version 2.10.1 RC (2009-12-06 r50690)
i386-apple-darwin9.8.0

locale:
[1] en_GB.UTF-8/en_GB.UTF-8/C/C/en_GB.UTF-8/en_GB.UTF-8

attached base packages:
[1] grid      stats     graphics  grDevices utils     datasets  methods
[8] base