The idea of a flash-based SIP client is very nifty. It should mean using a VoIP service when traveling gets that much easier, with no download and no NAT or router issues (you still could have sound card/microphone issues). It requires Adobe flash player version 9 or above, which may be a problem for some platforms.
But I have another question. I hate to be throwing wet blankets on this, but here we have another “anonymous” entity, this time in Russia – is it safe to give them the SIP credentials for our accounts? Who are these people? Where is the “About us” link on the website? The only contact info that I can find on the site is an email address firstname.lastname@example.org. Who are we giving our SIP credentials to and what are we going to do if they rack up of thousands of dollars in calls to our account? How do we know they are not selling our SIP credentials to some third party thieves?