Speed, Speed, Speed
I need my laptop to be light enough to lug around but being as light as possible is not a priority. An above average CPU and plenty of memory is ideal. A solid-state drive would also really help with starting up a large dev environment.
The trackpad needs to be good but the keyboard needs to be fantastic. I navigate with the keyboard whenever possible. The thing that slows me down the most is waiting, so things need to be snappy and streamlined. No bloat.
In terms of support, it helps to have some sort of instant chat available. Also, documentation for setting up and tearing down profiles must be superb.