The advantages are that you get all 64MB to run apps, and that having /home on SD means that all of your apps and settings will survive a reset...and more inportantly...a total loss of power.
I tried the cacko rom with /home on SD, and it was completely unusable in terms of speed. I thought it was the fact that I had a slow SD card, but decided to try tkrom. I have found tkrom 2 alpha 3 with /home on SD to be excellent so far. The device is extremely responsive, and I never find myself waiting around for apps to load etc. Maybe it's not quite as fast as using internal ram, but I really can't tell the difference
Have a look here for tkrom:http://www.oesf.org/forums/index.php?showtopic=2259&hl=tkrom
One word of warning. I was having problems with tkrom and my wireless CF. I have reflashed the device, but this time I have not flashed the async kernel. It has worked flawlessly since