Personally, I switched from Skype to
SIPphone. My reasons are:
- It's an open, standards-based protocol,
- There are compatible clients for Linux (I use linphone, open source), Windows, and Mac,
- You can call a SIP phone from a cell/land-line by connecting through a gateway number,
- Calling from SIP to cell/POTS is now also supported, by purchasing minutes (like SkypeOut),
- Toll free POTS calls are free,
- Free voice mail on missed calls,
- Free automatic call forwarding to multiple SIP numbers,
- Interoperability with the Asterisk open source PBX,
- Peering with IPTEL, EDGTEL, FWD, etc.; an increasing number of SIP service providers.
Hardware interfaces are available at the SIPphone web site, and are OS independent.
I think Skype's proprietary protocol and clients will hurt them in the long run. They simply won't be able to provide compatibility with all the applications and implementations that people dream up.