Other than reducing engine braking what other features does this clutch offer?

I find it strange that some find engine braking on a bike a problem wether it be on a road or dirtbike (4 stroke)
Taking this away I feel would take the the feel , control and fun out of riding.

I don't use one as I'm not fast enough to make proper use of it, but it allows quicker downshifts and doesn't lock the rear wheel up which give more control actually. Recommended for the track, probably not so much on the road.
It also wears the clutch plates out faster. Not sure that is positive.

they make a big differnce on the track, but not as much on the road. Just one less thing to worry about on the track when your trying to go fast.

I've had one fitted for about a year and I thought it would be only noticeable on track. But I was wrong. You can feel it working a lot of the time and if you are a quick road rider then you will feel the benefits every time you ride. It's a great bit of kit. It doesn't reduce the amount of engine breaking at all - the SD has masses of this, as do all big twins, and if you think about it - when your back wheel locks up and starts hopping about entering a corner unsettling the bike then you aren't getting the best engine braking effect anyway. What the slipper clutch does is smooth out that hopping and stops the effect of the bike traveling faster than the tyre is actually turning. It just means that the wheel can turn a bit faster than the engine for an instant and this makes everything smoother. It doesn't take anything away from your normal feedback and riding skills. I still have a finger on the clutch and I still feather it in many instances to get feel and feedback. But for those times when you bang it down the gears and maybe a gear to far it can really save you ass!