I just checked it out and here's my take on it...
The interface looks pretty cool. Microsoft has departed from it's Windows Live color scheme while designing Soapbox and it looks like they've done a good job. (Click the thumbnail below to check out a screenshot).
There aren't too many videos there yet though and I guess it's just because it's still in limited beta. I was amused to see that many of the videos were Microsoft or Bill Gates related. These were probably from the initial bunch of videos that Microsoft must have put in there to start off with.
The user interface is pretty intuitive as well. The player looks pretty good and handles well. One thing I liked in particular about the interface is that you can click away on the other parts of the page without interrupting the video that is playing on the side. This is a welcome change from the YouTube interface where you essentially cannot browse other videos while one video is playing.
The videos are limited to a maximum file size of 100 MB and the site accepts a number of different video formats including AVI, MPEG, MOV, WMV and even 3GPP (a popular video format used in mobile phones).
So, all in all, the site seems pretty good. Unfortunately, that's not sufficient to ensure success in the online video sharing space. There are plenty of sites out there that do all this and much more. And of course there are the well entrenched ones like Youtube. (Now that Google's behind Youtube, they are perhaps more formidable). Exactly how Microsoft plans to compete with all these sites, I really don't know. Of course, they will try to push it through their MSN network as well as their messenger and Live Mail. Still, I think they're gonna have a tough time amassing the kind of user base that Youtube boasts of today.-Prashant.