Stream protocols are not supported, but I'm trying to work on that.
a) the Mac bug have been detected and will be fixed on the next version (scheduled for this week).
b) to all: if you have strange problems, please e-mail me and I will try to find what the problem is. think that at it's working at least on my system and the reviewer's :).
c) I'll try to work on the extension page and add a little screencast.
d) to play FLV videos you need a FLV player, such as VLC (which is even portable).
e) you cannot (yet) download videos directly as AVI, as that's not between the formats provided. Anyway, you can convert from FLV to AVI using several tools (my favourite is the command took ffmpeg, but there are quite a lot of more graphically pleasant converters, just Google it).