Here in the good ol' US of A (
insert gratuitous 'boy' in southern US accent here 
) where GPS is used extensively I've found that having a Garmin 430 or 530 *dramatically* reduces the workload compared to VOR/NDB/DME only management. Even better with two of them! There are so many useful functions. Of course that presumes familiarity with the units
Even if test conditions preclude you from using the device as primary aid its ease-of-use makes it worthwhile to always set up as a secondary aid.
Another consideration is that it combines COM & NAV tuning heads. Some of our a/c only have '430s. No other means to tune COM & NAV. Can't switch the beastie off then... Others no longer have a DME so one has to set the GPS to use the relevant DME waypoint to be able to have DME data. Don't think that applies to UK a/c (yet) where I think DME is still mandatory? At least for Airways?
Still, it can't be too long before IFR a/c in the UK start appearing with 2 x 430s instead of the old kit.