Google Voice is pretty fantastic, but it does have a few snags. One inconvenience used to be that you had to give everyone a new phone number in order to use the features. That's no longer the case. Google announced a way to keep your number and still use some of the features. New users can choose whether they want to use Google Voice with their existing number or get the additional features of a Google number.
If you keep your existing number, you can use Google voicemail and related features. Google voicemail is compatible with following carriers: Alltel, AT&T, Cricket Wireless, MetroPCS, Sprint, T-Mobile, US Cellular, and Verizon. You can also use Google Voice for discounted international calls.
If you choose a Google number, you can choose your number by searching for desired number or letter strings. Using a Google number gains you free texting, call screening, conference calls, call blocking, and the ability to ring multiple phones at the same time.