My advice:
Make sure you have a good NAND backup of your current setup before you start.
Spend a bit of time reading others' experiences.
Choose the right version ... beta 4 and the new release 121 seem, from what I've read so far, to be for experimenters. I'm still using beta 1 because its absolutely stable for me. Others seem to say the same about beta3 ... I haven't had the inclination to change anything on my Zaurus for quite some time, because at the moment, it just works.
As usual, your mileage may vary.
Good luck!