The other day I was working in a coffee shop and their internet connection went down a couple times. Unfortunately, I was ssh'ed into another box where my work was. Fortunately, I was using screen. I figured my session would disconnect and be sitting there ready for me to reconnect when the link came back up. Sure enough, it was. Saved me a lot of hassle reopening my files and saving more frequently. Here's the article that describes how to reconnect to a lost screen session after your ssh session times out (not that it's that difficult, but I'm sure I'll forget and have to reference this).
Cezar: My only issue with screen is the terminal buffer. When using screen, it doesn't seem to fill the buffer. This is a hassle if you output large table lists using the mysql client or some such things.