Google’s acquisition of Grand Central a while ago was seen as a smart move by industry.  They took almost two years to invite fresh accounts to try out their new beta program, . The good thing about Google Voice (for that matter Grand Central) is that it lets users integrate all of their existing phone numbers and voice mailboxes into one account.  I have been using VoIP from Gizmo for more than 18  months.  I use a SIP device (Linksys ATA PAP2T) to connect my analog phone and make and receive calls as if using a regular line.  Gizmo provides the basic instructions to configure a SIP device.  BSNL blocks (I believe most of the ISPs do this) the SIP Port (5060) and fortunately, sipphone supports port 5061 also for SIP connectivity.  I also have a call in number through Gizmo so that, colleagues at US can reach me anytime. As far as mobile is concerned,  Nokia removed the native VoIP stack from N96.  However, fring is a reasonable alternative (except support for call mute, DTMF etc.)

Another pretty good collaboration by Google and Gizmo a week back added SIP support for Google Voice through Gizmo.  I just got my Google Voice and Gizmo integrated for both incoming and outgoing calls.  Google Voice call quality is amazing.  Its very easy to use and integrates well with your google address book.  Now, my next project is to get my phone, google and ovi to sync contacts and appointments so that I have a single list of contacts across all my collaboration services.