I'm currently using 1.21 and I find that eventhough my Xbox is in DMZ I still have connection issues with XBOX live. I dont need alot of bells and whistles but want a firmware that works correctly.
Im a little iffy about going to 1.30 at this point. from reading posts it appears a lot of people are happiest with v 1.11.
Feel free to post your comments on the different FW revisions.