I'm not really a bike computer guy, I'm not particularly interested in distance and how fast I'm going, but I do have Flight Deck computers on my two road bikes. I like them.
1. I like the virtual cadence function because it eliminates the second magnet, pickup and down the bike's frame.
2. I use a compact crankset on my road bike. The downside to a compact crankset is that you want to think ahead before making chainring shifts. The gear indicator function is great for that.
3. Flight Decks really come into their own on a tandem. The gear indicator is neat because I can't just look to see where the chain is and the virtual cadence is handy to know when to start pedaling again after coasting downhill.
4. Next to a bike that only weighs 18 pounds, nothing awes non-riders more than the little ovals to show what gear you are in.
The only downside (other than cost) that I can see is that it's easy to inadvertantly push the buttons. That's not so bad if you keep the two displays on speed and cadence so the computer won't shut itself off and stop accumulating your trip mileage.