I've started using this more and more recently. Sure it saves two pieces of paper -- and that's great, but it also seems to work pretty well in keeping me from carrying one more thing, or losing one more thing, or most importantly having to have access to a printer to go straight to security. And now that most of the airports that I visit in the US have this capability for Delta (my airline of choice) it streamlines my process.

I can check in from the cab, or from the office. I will have an SMS or email sent to me and then pull up the ticket on the browser as I am walking toward TSA (who have these scanners available).

Philadelphia seems to be the only problem now. When I come up to the podium I get a "sigh.. let me go find the scanner and see if the batteries are charged". So I usually have my tickets printed for the PHL leg of my journey. LAS, SJC, SFO, MSP, SLC, ATL, DTW and my other haunts are all no problem.