Compiz Fusion is very resource intensive. If performance is your goal I would
consider not using it. It works on my eeePC with 1 GB of RAM, but it slows it
down. I therefore tend to use it only on my desktop which has over 3 GBs of RAM
plus a 512 graphics card. If I want desktop effects on the eeePC then I use less
of them or run another desktop such as XFCE which is less resource hungry and
has built in compositing. I read that Gnome x.24, (the latest version) which
comes with Intrepid has a built in compositor. I have not used this feature yet
although I am running 8.10. I plan to try it out on my eeePC shortly.

I am not familiar enough with the specs of your computer to give a reason why it
bogs down with Compiz, but I would think that it might have something to do with
the amount of available RAM and/or video RAM. When Ubuntu slows down it is
usually due to excessive caching to the drive which is slower than RAM. This can
happen if your swap partition is too big and/or you are trying to do something
that is memory intensive. A large swap partition does not improve things if you
don't have the RAM to back it up. It can slow things down if it is too big
because the seek times are greater. The swap partition should be not any larger
than the RAM. If your swap file is the right size then I would look at getting
more RAM if it is lacking or if the swap partition is too large, either reduce
it or increase the RAM. If you feel that you have lots of RAM and a suitable
sized swap partion and it is still slow then I would look into whether it is
slow when doing other
resource draining tasks such as graphics editing or gaming. If not, then
perhaps Ubuntu could stand some tweaking and there are some tools to do this,
including taking advantage pre-loading which was built in with 8.04 but not
enabled by default.

This is just a shot in the dark since I don't know your system.