Much depends on the type of rod, how the duplon is used and the consistency of the duplon itself. If the duplon is too soft and squishy, I don't like it much. However, if it's too hard, it tends to go smooth and shiny with little use.
After a poor experience with an old John Wilson Avon that had the horrible abbreviated duplon handle and sliding rings (it compressed, went shiny and made the sliding reel collars useless), I always swore blind that I'd never touch a duplon handle again. However, after having a few cork handled rods with touches of duplon, I softened my stance a little.
I have ended up with a couple of small water/stalking carp rods with full duplon handles. Whilst they don't tend to spend a great deal of time being held, the duplon is just fine. I feel pretty much the same way about shrink wrapped handles. On rods that spend most of their time in rests, no problem.
One type of rod I'd never accept anything but the odd touch of duplon is on my float rods. There's a but to this one too. I'm a big fan of the Shimano Power Cork. It appears to be normal cork that's been impregnated or coated with some kind of polymer. It still feels and looks like cork, but it's less susceptible to staining, compression, and smoothing. I also have one float rod that has a handle and reel seat like a continental Bolo rod. I thought I would hate it, but it's not as bad as it sounds, looks a bit odd though. It's far better than any float rod with a screw up reel seat. I can't abide feeling the screw thread of a reel seat on the heel of my hand.