I was a SunRocket VOIP user until they went bankrupt and their hardware box became useless, so I thought long and hard about going with ooma last woot. I jumped in and haven't looked back.
Dropping the telephone part of my FIOS triple play service reduced my monthly bill by close to $30 when you include all the taxes, fees, surcharges, etc. Ooma costs me $10 + sales tax /month for premium service with 2 lines. One is 'dedicated' for home use and has its own distinctive ringtone so everyone knows which line it is. If you want, you can dedicate a phone to one line only so, for example, a teen or in-home business could have a line that nobody else 'accidentally' picks up.
Another great feature is being able to simultaneously ring my ooma phone handset and my cell phone. I give out my ooma number to everyone and have ooma forward it to my cell. If I'm home, I pick up the ooma phone. If I'm out, I can either use my mobile phone or let it go to voicemail. VERY convenient! You can have it forward after "X" number of rings, too.
When their Android app comes out next week (or thereabouts), I'll get that too. With premium service you get 250 free minutes/month and since I'm on a cheapo Virgin Mobile $25/mo plan, the extra minutes (using wifi), will be very welcome.
All in all this is a great price, a great product, and an excellent value. If you're still sitting on the fence... go for it. Worst case: Sell it on Craigslist if you're not happy.