I feel your pain guys, but I am honestly on a 100% VoIP setup right now. I'm using GrooVe IP as my primary and the 100 minutes as a total backup. I do have the occasional issues of choppy calls, static or not working well while moving or lower quality signal areas, but I'm at about 95% success rate right now and like I said, for those emergencies, I'll just have to call via standard dialer.
For my Groove IP Settings on my Exhibit II I have the following:
Speaker Volume: -5 Microphone Gain: -6
Keep Screen On: Yes
Audio Processing: Yes
Synchronize Voice: Yes
Audio Routing: Yes
Mic Buffer: Large
Mic Source: Auto
Partial Wake Lock: Yes - This will get rid of the issue where the call goes to voice mail before it rings through.
I've totally messed with just about everything possible in the 20 days I've been working on this little "completely VoIP" setup and Groove is the second best option that I've found. Skype is by far and away the best voice system, but you have to pay an additional $85 a year to use their Skype Number and Unlimited N.A. calling plan. You also do not get free texting via Skype so you'd have to set it up where your GV number forwards to Skype - then backwards for out calling. It would work, but more steps.
I think GV - as long as it stays free - is a great option for combining numbers. GrooVe IP is by far the best plan for making calls from GV so far. Much stronger than SIPDroid and until there's a native app from Google, it's really the only good option.