Their problem is branding. When you think "realtime video streaming online" does the word "justin" even enter your mind?
http://www.google.com/search?q=stream+online - nowhere to be found;
http://www.google.com/search?q=video+stream - over halfway down the page
It's quite sad. justin.tv's infrastructure is better than their more popular competitors, but performance doesn't always win the mindshare war.
I don't think they'll have much trouble establishing market share once they launch.
Justin.tv should consider an updated business model where they branch out their video streaming products and rename them to increase comprehension for consumers.
Justin.tv is kind of a dark horse -- ustream may be better known, but Justin.tv is actually bigger. The Justin guys can probably explain this better than I can. :-)