Depending on what aircraft you are flying, you may get some spikes to the inverters when you start.
Not so long ago I got given a brand new EFIS for Xmas. Fantastic equipment but I agree with 800 - get to know your way around it if you are going IFR. A couple of little tricks here and there.
The beauty of it is that you can play with it on the ground without starting the engines.
Warming up??? You just have to wait until it's done. The time you are waiting can also be due to the gyros spooling up as well.