Probably due to the crappy rear tire I have on now, but it seems that if I even think about using the rear brake on down hill slippery stuff, it locks up and tries to pass the front tire. So I don't use it on those occasions. I keep 90% of downhill braking on my front brake. The rear brake works fine on rock and dry conditions though.
It is my hope the hand operated rear brake will assist me in the following:
1. On hills I fail to climb and engine quits, (meaning I crashed on the hill climb), and outfitted with an auto clutch, the only thing holding me on the hill is my front brake. There is no engine compression to hold me on the hill like a regular clutch operated bike. Having both front and rear hand brakes will help me get the bike situated while still having both feet able to touch the ground.
2. Brake sliding on right hand turns where I would like to stick my foot down would now be possible. Tight switchbacks are my focus here.
3. Adjustment of the rear brake control to be operated wtih two fingers like my front brake may now be possible. Just the thought of being in as precise control of my rear brake as I am with the front brake is very appealing.
As Smit-Dog points out though, arm pump is a concideration. However, I've never experianced arm pump on my left arm as I am a left hander and much stronger on that side. My archery training and bow hunting has also aided in developing some strengh in that arm as well. I do experiance arm pump in my right, throttle side though. Usually within the first 30 minutes of riding, then it goes away for the next couple of hours. Riding longer and it slowly creeps back as my hand starts to cramp up.
No doubt about it, I'm holding off on the changeout until I get some time to ride outside of the enduro season. Besides, I would like for some more folks to try out the auto clutch on my bike and if the hand brake is on, then it's more likely the brake will be too distracting.