AT&T has significantly increased the effective cost of our family plan, partly through a covert and possibly illegal 2009 contractual change. It's effectively a 20% increase that's come due now.
I'm looking at alternatives. The most promising two are PAYG SIMs and, paradoxically, buying new iPhones on contract and selling them to China to fund use of the kids' old out-of-contract-but-forever-carrier-locked iPhones with the mandated $15/month AT&T smartphone tax.
Another option is to replace texting use. For example, we could sell the old 3Gs, buy iPhone 4s, have AT&T turn off texting (they will do that, albeit reluctantly), use iOS iMessage  among us, and use Google Voice for SMS as needed . Dropping our $30 text and mobile-to-mobile plan would cover the cost of AT&T's covert rate increase.
Facebook Messenger is a cheaper option, particularly if one is going to use Google Voice for texting and disable texting on all phones.
So I ran some tests on my 4 and my son's 3G. (I'm still on iOS 4, waiting for at least iOS 5.01 and for all my apps to get settled in). Alas, Messenger needs work.
It's a slow app that takes a while to load. Messages are very fast (WiFi), but one message got stuck in the queue for a minute (!). It took only a few minutes of use to turn up bugs and performance issues.
So initial impressions are mixed, but we'll keep testing. I'm also researching alternatives. It's too bad Google is famously incompetent at iOS development (where did all their smart people go? Has any company flamed out so quickly?)
- Top 10 Clever Google Voice Tricks (this is an older article, but it's brilliant. Deserves a post of its own).
- Free alternatives may cut into text messaging profits - Los Angeles Times 8/2011 (Facebook, iMessage, TextPlus, Google Voice)
- textPlus – Free text messaging and group texting
 $30/month + fees ($36) texting plan over two years is $864, enough to pay for two iPhone 4s and $15/month data plans assuming we make some money from selling the 3Gs and of course the 4s have higher resale values.
 We have a (free) family Google Apps domain, every user has Google Voice.