Be careful! If you have an EVO then you have a Sprint plan. GOOGLE VOICE CALLS ARE NOT FREE!!!! All Google Voice calls are routed through landlines by Google first before connecting to the person you are calling. That message that goes "This call is free" DOES NOT mean free because it inst using minutes. It means its free because its within the Continental US and you are NOT being charged your GOOGLE minutes (yeah, that balance .10 cents thingy that you can see in the web browser).
I used to be under the impression that Google Voice was full VOiP but it isn't at all! When I first got my EVO I was super gung ho about setting up my EVO with my GV account and giving out my GV number instead of my Sprint number. So after about a week, I was curious as to how to check my plan usage from the phone and find out its *2. I called it and it said I used 170 minutes from my 450 minute plan! I almost had a heart attack! I was like WTF, I'm using GV!!! SO I went to the GV support forums and found out that any call you make using Google Voice is going to count as a land line call by Sprint which means its gonna come out of your minutes!
I hard reset my phone and just gave out my real number and disassociated my phone from my GV number completely.
If you have the $99 everything plan, you can use GV all day long cause you have unlimited everything. But if you have the 900 minute or the 450 minute everything plan (which I have since I hardly EVER call landlines), you shouldn't bother using GV!
Now with that said, texting with GV is free on all accounts.