> they bring absolutely nothing new to the table.
they are using the open SIP protocol. this can be a big advantage
> No webcam support
you are wrong. HD quality video is there
> Windows only
yes in case of mizuphone. there are other alternatives for other platform (and all sip client can communicate with each other with no problem. can you make call from yahoo to skype?)
> Proprietary.
there are also opensource sip applications
skype is also proprietary
>Costs money
Yes, if you buy from mizutech. but from voip service providers you can download it for free
>the GUI is kinda ugly
work in progress