We use a Tracfone and we've had decent results.
The pros: CHEAP (if you don't talk a lot and don't have the urge to take pictures/surf the web, etc.). We also usually always get good reception.
Cons: lame/unattractive phones, the customer service is HORRIBLE - you will never speak to a representative in the US, and if you have a problem it may take hours/days/weeks to get it resolved.
One personal story ... One time we bought a new TracPhone + $200 worth of minutes. 15 minutes later my son threw the phone in the toilet. We called TracPhone, they sent a new card for the phone, it didn't work, hours were spent trying to fix the problem, they 'determined' that we used all the minutes and refused to refund the money, I filed a dispute on my Discover card, TracPhone never responded, Discover refunded the $200 towards minutes. MORAL OF THE STORY: Always pay with a good credit card in case any issue arises.
At home we also use a MagicJack ... kind of annoying, but it gets the job done. You can spend a long time talking and pay very, very little.