I am coming around to really liking Google Voice.  Google Voice is more than just another phone number, it has:

-web based SMS
-voicemail transcribed to txt. (very slick!)
-advanced call routing/handling, including time based clauses
-easy to use Gmail like interface
-integration with Google Contacts

Google Voice centralizes all of my SMS and voice communications with the added benefit of using my Google Contacts.  I can offer a single phone number to callers, change where those calls ring on the fly, block callers and give priority to friends/family.

At first I was not impressed with Google Voice, now that the dust has settled, I am definitely a fan.