In my experience, Jitsi is not stable enough for a 1.0 release. I reported to the list earlier that I tried to remove a contact from a group and the software froze. When I re-opened Jitsi the contact list window did not appear at all. I re-installed Jitsi and restarted it and the contact list still did not appear. I opened Adium successfully and it's connected to the same XMPP accounts, and it is stable, so it's not a problem with the server I think.
I have had the experience of having a video call with a Gtalk user which worked well. However, when I terminated the call in Jitsi, the other party reported (via IM) that they could still see my video feed and my audio feed, so I had to shut down Jitsi completely to get the video and audio to stop being sent.
I reported also to the list that Jitsi consistently freezes when I wake my computer from sleep state (OS reports "Not Responding").
I have this experience on two different laptops running OS X version 10.6.8.
I would really like to use Jitsi regularly. The feature set is wonderful, but I have not recommended to anyone else because it still has major bugs that I've listed here.
In addition, I'll put my opinion out there that the user interface is excessively complicated. Normal, non-technical users don't need level readouts for the local mic and remote audio levels on the main UI.
The IM screen format could be improved as well. The timestamp text could be smaller, or less visible, or on the right side of the window, to make it easier to read the chat flow. Check Adium's UI for an example, or even the web-UI for google's web jabber client integrated into GMail. The time stamp is nice info, but shouldn't be in the user's face, because that isn't the focus of the interaction while chatting.
Also, one developer mentioned that it was an intended feature that when you answer a video call the local video is not sent to the remote user until you specifically enable it. I understand the logic behind this design, but users are not accustomed to this behavior (mainly because GTalk, Facetime, iChat and other mainstream apps don't do this).
I think if you want to keep this behavior, have two answer buttons that are clearly labeled "Answer" and "Answer without video" or "Answer Audio Only"
I hope these suggestions are useful to the Jitsi developers. Like I said, I love the feature set. You guys have done a great job so far.