As a current 4G customer, I can say this has been the most frustrating 6 months. It's been well documented their LTE network has been sketchy from the start:

4G launched in Dec 7th 2010 and this article ran a week later about issues already showing up with handoffs between networks: http://bit.ly/td1XQT

Another article from April 29 2011 about an earlier 4G outage: http://bit.ly/v8zJUZ

I'm not surprised this happened and will be returning to 3G. Clearly their 4G is not ready for prime time yet.