I've been riding forever in snaffles or rope halters. I've done compeditive trail and I primarily trail ride and ride in the mountains. I don't love the idea of my horse having a bit in its mouth for 8 hours, or having to exchange the bridle for a halter during breaks, So I started riding in a rope halter. I find it takes a couple sessions to get them sensitive and flexible bitless(just as you would train in a snaffle) But that they like it just fine. Not very nice looking mind you.
Then last year I had a paint mare who had a very shallow pallet(could not stand a regular snaffle, it poked the roof of her mouth) and her previous owners just kept riding her in the wrong bit, getting rougher and rougher. I thought she would be much happier bitless(and I wanted somthing that looked like a bridle, not just a halter), so I started looking for bitless bridles. Both her and I HATED the dr.cook/natural style bitess. I'm not a fan of mechanical hackamores, so I ended up getting a local guy to make me a side pull. It looks fantastic and worked great on her.
Lately I've been using it on all sorts of horses, and after a session of flexing with it on, they seem to work as well or better than with a bit. I'm not going to stop using bits altogether, but I do see myself using the side pull the majority of the time. I even found an article about a very compeditive event rider who prefered to use one cross country.
For those of you who have used them, What do you like and what do you dislike??