I plan on getting one. I will probably sell my one x to fund it or see if I can get at&t to let me do an early upgrade to get one since I bought the one x about 3 months ago. Maybe a Xmas present to myself.
AT&T ETF Policy is here:
Early Termination Fee Policy
So long story short, if you sell your current phone, you need to get 325 (minus about 30 bucks for "time served") just to cover the ETF, (or about $295), then you have to cover the up-front fee on the new phone which will probably be $199 (at least for a while). Note: I'm guessing here, because I don't think AT&T has announced a price yet, but all high-end phones seem to start at $199.
So you need $495 from your current phone to get the upgrade with no out-of-pocket.
No Commitment pricing on the current One X phone today from AT&T is 499.
So most people won't pay you any where near 494 when they can pay 4 dollars more and get a warranty, or
just pay 99 bucks with a two year plan.
So I suspect you are going to have to kick in a little money for this upgrade, probably $150 or more likely $200. If you get the ETF from your sale of your current phone, that's probably about as good as you will get.
Might still be worth it for you, but its not for me. Maybe when LTE is more widely deployed.