If you consider when Flight Deck (FD) was offered (I think around five years ago), it was ahead of it's time. It offered both cadence and mileage data without having to install a chainstay sensor. The computer was sealed with epoxy on the backside to render it waterproof. Just the ability to show your ring and cog (particularly if you rode a triple), was worth the price of admission.

Today, I use a Sigma Rox 9.0 and haven't been more pleased. I love the slope, ft climbed, and calories burned features, plus HR too. But I plan to install FD also to get the gear info, particularly on my triple bikes. Plus I can set that in kilometers while my Rox reads in miles, as sometimes I like to see my km/hr speed too. What's nice is the FD and Rox sensors don't compete for space on my chainstay, as the FD sensor mounts on the front fork.