I have just tried out another new Adobe Flash-based video IM program, SnapYap. Like other such flash-based programs, there is no separate program or client to download and install on your computer. That means that it should be platform-independent, and indeed I just tested it with a call between my two laptops, one running Vista and the other running Ubuntu, and it all worked very nicely.
Spontaneous calls with others who are not registered SnapYap members are easy; when you register you are given a URL which you can send to anyone else, and when they go to that address it starts a SnapYap call with you - if you are online, that is. If you are not, they are given the option of sending you a video message by email, which is a rather nice touch. The recipient actually gets a URL to the video message, which then plays in a browser as well, so there is no worrying about video formats, media players and such.
To call other SnapYap members, you currently need to know their SnapYap username, which can be a bit tedious if you have very many contacts. There is currently no "friends list" or directory, but I have heard there will be a new SnapYap release within a few weeks, and I suspect that might be one of the things they are adding.
You have the option of either calling or sending a video message to another member, and if you try to call and they are not available, you are again given the option of sending a video message by email.
The audio and video quality in a call seem reasonably good to me - typical of flash-based video chat, at least. Like the other flash-based chat programs (TokBox and the web clients of ooVoo and SightSpeed), the audio/video data does not appear to flow from peer-to-peer, but rather through a server somewhere on the internet - at least, on my tests here, when I connect two systems which are on the same subnet, I can see the data activity not only for those two systems, but also for the internet connection.
During a video call, the incoming and outgoing video are presented in equal sized, side-by-side windows. I did not see any way to reduce the size of the outgoing video preview to make more room for the incoming video. There is a "Full Screen" button, but what it does is not quite what I would consider full screen. it basically expands the SnapYap main window to fill the entire screen (without browser borders), but because the incoming and outgoing video are still displayed side-by-side, the actual video view you get is still quite a bit short of a full-screen view.
There doesn't seem to be any way to make multi-party video calls, at least yet. Trying to call someone who is already in a video call results in the "user unavailable" message, and clicking on the "call" button while already in a call says "starting a new call will disconnect the current call". However, the presence of that button during a call leads me to suspect that they might be adding multi-party calls in some future release.
In summary, SnapYap looks like a nice addition to the Video IM space. It is pretty much what it claims to be - a video communication too which is as straightforward as possible. It will be interesting to see where they go with future releases.