I just set up the kernels & recoveries for the samsung intercept & acclaim to convert from rfs, on both of those what I've recommended & people have liked is going to ext2 for system, and ext4 for data and cache. Ext2 is only volatile on writing, and system is read-only 95% of the time, so the chances of corruption that way are low. The problem we may run into is the same problem I had trying to resize the partitions, the bootloader on the hero, evo, & others that allow resizing is unlocked, I'm not sure if ours has been.
Can you tell us how you did that then? I know how to enable different filesystem support in the kernel, but I'm not sure how to get the recovery to convert the filesystems.