ZFS with FreeBSD updates

Hi all, I plan to set up ZFS on a 1.5tb drive soon and was just wondering how seamless OS updates are. Future versions of the OS will obvious have better ZFS support. When I update, will I have to reformat to take advantage of those features or will they automatically apply to my existing ZFS volume?
You will have to upgrade your ZFS volumes, which is a non-destructive process.
zpool(1) upgrade
is what you need to do. For example there is a newer version of ZFS in -HEAD than in any of the branches, so once that code filters down to you in a release, you will be able to run that command to upgrade the metadata. Obviously you will want to backup the critical data and test it elsewhere if you can.