An ex-girlfriend did it. Definitely reality and not just crazy talk.
There are some obstacles...
initial time investment (hard if you work 60 hours/week...good if you work at home or have free time)
having a household toilet mostly tied up with the cat's stuff (at least during the training phase)
random cat behavior (your cat might decide it is fun to flush the toilet...and flush and flush and flush 20 times in a row from 3:00-3:10 AM just because it particularly enjoys the sensation)
The biggest drawback I saw (from witnessing ex-girlfriend's household) is that not all cats will learn. Most will, but if you have three cats then your "slow/skittish/whatever" cat probably won't learn and even with two out of three cats toilet trained, you still have to keep a traditional litterbox for the one who couldn't adapt. So what is the real advantage unless you get ALL of your cats successfully trained? My advice is to start with your least intelligent cat and work up.