I made several posts on cleaning related type threads about the Otis system. It is truly the most versatile system I've ever used.
Since you haven't used it yet, follow the instructions carefully. If not, you can get patches either stuck or fall off the brass tips. I also don't recommend using the 2" panoply patches on the smaller calibre guns, .17 to .22, use the small caliber patch they have out for those.
Other than that, you only need 2 patches for every caliber gun you own or will ever own.
I use it to clean all the guns I own (which isn't many, but calibers range from .22; .30; 9mm/.38; .45; 12GA
. Only one guy I've heard so far said to someone else to not use Otis while cleaning an AR. He says it's good for field expedience only, but if it's good for that, why not just spend more time on it at home?
You should still keep straight rods around just in case you get any patches stuck in the barrel as mentioned above. One other thing, they advertise 6 uses for each patch, but that isn't really the case. It's more like 4 max.
Still, the pros far outweigh the cons, and once you start using it properly, you won't really need anything else. Most of your existing brushes will work with the flex rod because they have an adaptor for the threads to screw on.