Its funny, but half frame is an actual full movie frame, 35mm is a double frame of that. So technically half frame cameras are full frame, and 35mm cameras are double frame then! lol
I really do like my Canon Demi S, its the only half frame camera I have. Its nice for sequences 2-3 frames wide. But at times its challenging to print. I use an adjustable glass neg carrier to fit them, and many times you have to block out a frame when doing a sequence and apply different times and dodge/burns. Then lens on it is ok, but large enlargements are impossible, just not enough information to print big with.
Also like others have pointed out, 72 frames can take awhile, esp when you are stuck on the same film speed or a small range of film speeds like 100-200, or 400-800.
I would like to get another half fame camera, either one like a older version such as a Mercury or a version like the Pen F/FT. Those would seem fun to use.
I think the downfall is that smaller full frame 35mm cameras were invented that were smaller and better than these half frame cousins. The Olympus RC I have is about the size of the Demi, but its much easier to use, with lots of upgrades, and most importantly the lens on it is very good, much more so than the demi. The focusing is much more accurate as well, rangefinder patch vs zone.
Now, time to get back and finally finish my 72 frames lol, its the only camera I have to use a bit of tape to write on the loading date, and film type/speed im shooting at.