Marci and I have found CCR to be very useful even in very shallow caves like Peacock.
For example, rather than doing two dives that are each 2 hours long, we'll do a single dive that is 4 hours long. There are some significant advantages.
1) We only haul stuff to and from the spring once.
2) We have little or no deco with a PPO2 of 1.0, while we'd almost always have some deco on dive 2 when doing it OC with 30%-32%.
3) We only swim the front parts of the cave once. Some sample dives:
a) swim from P1 to the crypt, play around in the side mount line below the crypt, then swim to challenge and play around in the offshoot tunnels up there before exiting.
b) enter at OG and then swim the Martz off shoot, then swim each fork of the distance tunnels.
c) enter at OG and swim to Woody's room and do all the lines in the area before exiting at OG.
d) enter at P1 and swim the water source tunnel well off the map, then come back and swim all the side passages and Ts along the peanut tunnel on the way out.
e) enter at P1 and swim the wishbone to the Crypt, then back up through the dark water tunnel, oslen bypass, back down the peanut side and through the cross under tunnel.
All of those dives could be done OC, but it would require a lot of staged gas, and with no scooters in Peacock, some of them would require some set up dives. Swimming 4 hours while hauling stages is work, while carrying a stage maybe 1000' to position or reposition it is easily done and very enjoyable.
We do use a couple stages, but they are strategically placed and then just repositioned as needed to support the next day's dives. Dive a full week and they are still full and have been carried only a few thousand feet in total.
4) Best of all, with the 4 hour dive plan, we get up late, eat breakfast slowly show up at the spring around 11am, get great parking even on busy weekends as peopel leave for lunch and gas for their afternoon dives, gear up slowly get in the water by noon, get out around 4pm and are done for the day by 5pm. It's turned cave diving back into a relaxing vacation without sacrificing dive time, and the quality of that dive time is higher.
Slightly deeper caves like Ginnie or Little River are where the deco benefits really start to show, allowing longer dives with less deco.
5) CCR also greatly increases the comfort level in tight, silty cave passages and we've found we can go slower and dive cleaner, due to both lack of percolation and the ability to swim very slow in snug spots without sweating the gas plan like we did on OC. CCR gives you lots of time relative to OC. Basically the dive gets turned on the bailout gas limitations but with a couple of strategically placed stages those limits are generous, even without getting into a team bailout situation.
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On the other hand, it's not for everyone and it's not something divers should be getting into until they are very proficient in cave diving. Not just the number of cards, but rather extensive experience on top of those cards. As noted in some of the above items, CCR allows you to get into some places you probably would never go in OC - and that creates the potential for an inadequately experienced diver to get in way over his or her head.
Avoiding that requires not just training and experience, but also the ability to accurately and realistically assess your true ability to dive the conditions you'll encounter and the discipline to veto those dives that exceed your ability, or to turn the dive when you've encountered your real world limits. It also takes significant knowledge to fully understand the rebreather as a system, and to understand its flaws, it's vulnerabilities and understand how to address them when something goes wrong on the dive.
Not everyone who can plop down the cash for a CCR has the knowledge, the skills, or the necessary level of discipline to actually dive the dives they end up doing, and that's where people start dying.
