It's a free app but I do have one big qualm about it.
I've recorded two videos so far and each one of them has video and audio breakup at the beginning. My first test was outside and on the 3G network:
And here's my second test using Wi-Fi:
Compare that to the quality of the jailbroken Qik app:
I did notice that the overall sound on the Ustream app was better, though.
You can connect your Ustream app with Twitter on your iPhone but to connect it with Facebook and YouTube, you have to go to the actual site which is a little inconvenient. But, once you have it set it should be okay.
Another great feature of the Ustream app is the ability to record video straight to your iPhone - a feature that the iPhone 3G has NEVER had until now (without jailbreaking). However, the videos appear to be only playable through the Ustream app. Still, that's better than nothing.
It looks like Apple is finally caving in to giving ALL iPhone the ability to record video without jailbreaking. It seems that Qik has also resubmitted its app for live streaming so I'm sure we'll be seeing that very soon.