Google Voice has a bunch of nice features, and integrates very well with Android phones, but I gave up on it after dealing with too many cases of dropped audio during calls. (I have a very low tolerance for any service, free or paid, that screws up communication with my clients.)
I ended up porting my Google Voice number to a commercial service, Toktumi:
There are some things Google Voice does better than Toktumi (particularly contact management and Android support), but Toktumi doesn't drop my calls, supports VOIP, and lets me completely block callers that withhold their Caller ID information. I've been switching over to iOS devices, and I've found the Toktumi "Line2" apps to be better than Google Voice on that platform.