The topic of ADF and DME integration in the G1000 seems to be a source of misunderstanding, so I will try to make the situation a bit more clear for anybody.
At first, you must know that ADF and DME are not part of the standard G1000, but are options. One bad consequence of this is the way they are integrated. At audio box level, there are keys for turning their audio on or off, but all the rest goes through soft-keys and the FMS knobs.
Typically, tuning and ADF frequency needs the following steps:
1) Press the ADF / DME softkey
2) Go in the frequency box
3) Change the frequency with the FMS knobs
4) Press enter to validate the new frequency
5) Press enter to activate the new frequency (flip-flop)
6) If needed, use the FMS knobs to adjust the audio volume
Not exactly simple, isn'it ?
The same kind of procedure is needed to switch DME from NAV1 to NAV2 receivers. Because of this, the school where I trained decided to always fly with the DME coupled to NAV1, to avoid too complex and lengthy manipulation in flight.
Something else that is not possible with the G1000 is to have two simultaneous display of the ILS. I know many people tuning NAV1 and NAV2 on the ILS while flying with classical instrumentation, so as to be able to continue in case of receiver failure during the approach. As the G1000 has only one HSI, this is not possible. Nevertheless, you can tune the ILS on the two NAV boxes, and in one fail it is possible to switch the HSI source with one soft-key click.