My partner has a single rack of these and I got chance to try them out the other day in Tuolmne meadows on a route called Phobos where it helps to have extra hand sizes.
I normally climb with camalots but I've been eyeing these DMM cams for a while, the extendable sling appeals to me, and I generally have very high opinion of DMM. Have to say though after trying them I don't love these for a couple reasons
the stem is too short. The short stem means trigger is deeper in the crack, and harder to clean. it's more likely to get stuck than camalot which has a longer stem and trigger is set back a ways.
the lack of a thumb loop, makes these feel super awkward, when placing. especially for the medium sizes and up. which feel off balance and front heavy and floppy aroundy.. it's surprising how much the thumb loop helps when wrangling the larger cams.
Extendable sling length. When I first saw it I thought it would be a great feature. Unfortunately it's too short. Fully extended it is no where close to the length of a single length sling. So you are still going to have to carry a bunch of slings when rope drag is a problem.
Re-racking when when sling is extended sucks & if you rack it with the sling extended it's hanging down by your knees getting in the way. it's a pain to have to stop and re clip the sling back into the cam when cleaning. Harder than throwing a single length over your shoulder.
I know this sounds like an add for c4's, I don't want it to be, but when I was climbing with the dmm cams I found myself wishing for my c4's. I'm probably going to refuse to use these next time. Nothing sucks more than not being able to clean a cam because the trigger is too far in the crack.