This is something I wrote today, when someone asked me about VoWLAN handheld hardware:
To be honest, the VoIP space is over-saturated at this point. I did a fair bit of market research and analysis in this space when I first moved back to Vancouver, but there are just too many people in the space right now. We'll see a die-back here just like we did with the Data CLECs -- NorthPoint, Covad and Rhythms are all dead and gone, even though their stock went from 70¢ to $170...
Where to focus on the VoIP space? Software. For VoWLAN, a killer application would be localized detection of other handsets and buddylists, etc. This is kind of like a walkie-talkie plus instant messaging.
So, needless to say, I'm focusing on web applications and collaborative tools. Hope that little rant was useful.
I skipped adding a bunch of other stuff regarding UI design. Like, Skype is winning as much because of their usability as their technology. But if someone built a softphone with a decent UI that worked with open protocols...perhaps that is the same as asking for Linux desktop usability: it's not quite there yet.