Ok, as someone who hasn't yet converted to ext3, but will as soon as I upgrade the kernel, there's a couple of things to realise. Firstly, as far as I know, an ext3 drive can be mounted, even if you don't have ext3 support in your kernel. You won't get journalling, but other than that, it'll work just like an ext2 drive. As for the conversion, I don't know what the programm's called, but you can convert ext2 partitions to ext3 in place, without touching the data. That's the main reason, as far as I can see, to use ext3 over reiser or any of the others, particularly if you don't have anywhere else to copy the data before converting the drive.
