I have been a Skype user for a while now, long before its purchase by ebay. It has worked well, particularly among more business oriented folks such as portfolio company executives and investors. I think it has caught on with the younger generations as well. Some of the problems I had with Skype were that there was no free voicemail, that you were not given a number that land users could call you at (you can pay for this), and that you have to pay to call non-Skype users.
Along came SIPphone! I have started using Gizmo by SIPphone. To all my blog readers, I encourage you to go to SIPphone and download the Gizmo. It's exactly like Skype but better. Same interface, same everthing. Here are some differences:
1. Free voicemail - They send you an email with a .wav file of the voicemail.
2. Free number - You actually get a number that anybody can call you at (although it has an obscure area code, you can pay for a premium number.
3. Cheaper - Gizmo Out calls are 1 cent per minute to anywhere in the US
4. Multiple network calling - This is the major differentiator and appears to me the most compelling reason to use Gizmo over Skype. Gizmo and Google Talk have an agreement for free VOIP within the network. Gizmo also can talk for free to several other networks and universities such as many University of California campuses.
While I believe the VOIP wars are just beginning, the philosophy of SIPphone is the OPEN network and I believe that this is always a better strategy than the adopters of the closed network. If anybody has any criticisms or comments on Gizmo by SIPphone, please let me know.