Duo's are awesome. Here's my experience:
I have run a tight creek with another experienced paddler and we aced it. Teamwork is everything. Comparable paddling style was also beneficial.
I have taken beginners out on solid class three and depending on their preferences for excitement, they've almost all loved it. Those who were less "excitement-oriented" said they still liked it, but they said they'd have preferred more scenery and less excitement.
The weight of the beginner up front is critical. If the person up front out weighs you and doesn't do things right, you might end up swimming. I've only swam once with a lighter weight paddler up front, but I've never felt sketchier than when the guy up front outweighed me, wouldn't take my instructions, and let go of his paddle everytime we leaned into something....so maybe don't take your old man out in it
. Moms, girlfriends, and skinny male friends are great passengers. If you've got 40 lbs on someone, they can lean anyway they want and you're probably going to compensate just fine.
I've taken my duo on some self-support overnighters with non-boaters and they were PSYCHED. I could also see using it solo with a hatch cover if you needed to haul a lot of gear or something. Say like you wanted to do a climb across a river. You could ferry your partner, then go back and ferry the gear, too. Say you wanted to bring your chainsaw, whatever, you could do it fine in the duo, but you'd have to paddle Grumman canoe-style since you're not centered. Probably wouldn't want to run something too squeezy like that unless you're a Grumman OG.
Lastly, the things front surf like beasts. Find a fast green wave and get on it. All you do is rudder. If it's steeper you can perle the shit out of the bow and dunk your front passenger, too.
Anyhow, get one. They're fun and you'll love it. You kids will love it. Your friends will love it. Your wife/girlfriend will love it. Just do it.