I did a flight in a G1000 equipped 172 recently and found it fantastic for navigation, but very difficult when it came to the circuit and landing. I think the main reason was it's tricky to judge altitude changes required on the tape as opposed to the traditional round gauge.
Ie. It's easier to see: I'm now at 2100' and circuit height is 1500' so I need to loose just over half the gauge, rather than working out 600' in your head when coming into a busy circuit area.