Well I've been using "Sipdroid" on my HTC Incredible 2, for the last month. It's been working quite fine. Easy to set up. Allows up to 2 sip accounts that you can switch between the two. Will allow both incoming. I only have a few places where cellular service isn't available; but a WIFI signal is. E.g. Basement of one of the office buildings I work in sometimes. Sometimes a site in the middle of no where. We have internet and wifi but no cell signal. It has come in handy.

Also, when I'm expecting an important call, instead of going online or to my home phone and forwarding it or doing a simulring; I simply turn the "SipDroid" app on in my HTC Droid and it receives the calls too. Much faster and simpler. Then I don't have to remember to turn off forwarding, simulring, etc...

The only issue I had was a recent trip to Peru. Apparently they block a lot of ports. I couldn't get any Cell service, "Without paying a lot", but I could get wifi. The calls back to the states was very choppy. It wasn't a voipo thing because the exact same thing happened when using Skype. But in the states, it works great. I was recently at a local airport that believe it or not, had almost no cell signal. But they did have free open WIFI. One click and Sipdroid made a perfect call to my wife at her work. "She was a little confused when she saw our HOME Caller-ID. She thought I was home when I called. She panicked. I told her I was at the destination airport and all was fine. Told her how I made the call being the cell service wasn't available. She giggles at me being a techno-geek; but she admits it comes in handy. "Except last night when she saw me with my NEW Android with the back cover off and a soldering iron in my hand". She was speechless. I told her I was improving the GPS reception. She just covered her ears and walked out. LOL

Anyway; SIPDroid seems to be working fine. I might give CSipSimple a try. Thanks for the info. mike....