I've run auto lockers front and rear, detroit rear and arb front and now arbs front and rear and my take is this:
For nasty road street driving the arbs are really nice, especially the front. In fact, I would consider no other way since a detroit in the front is terrible on bad roads in 4wd.
On road, a detroit rear is typically livable depending on your tolerance for locker feedback and the type of truck it's in. I'm usually fine with the detroit in my sub and didn't have problems with the det. in my K5 as long as I had some rear weight in it. Mixed traction conditions like snow/ice in one wheel track and dry pavement on the other is BAD with the detroit since it drives off the wheel on pavement and when that switches to the other wheel, your steering correction for the yaw switches to the other direction and it can be a handful.
Offroad, there's a lot of stuff you can do with a selectable in front, like turn easily to name one thing. I've used it to hold on nasty side hills, climb ledges without slipping sideways, hold me in place on slippery rocks, etc. Higher speed offroad is way better with the open front also.
Offroad, I haven't seen as much benefit with the arb in the rear as the front but there has been a few time I've used it to do things I couldn't do otherwise.
I haven't had major problems with the ARBs, I run the heavy line kits and route everything nicely so the lines aren't an issue. I periodically replace the relay but it's an unsealed relay in an open vehicle, I need to put in a sealed unit. My wiring harness is from my original install in '98-ish and I've had to re-wire switches (just using toggles now) but otherwise it's been no problem. If you install it well and take reasonable care of the compressor, it'll serve you well.
I have had one compressor crap out and we just plumbed a power tank to pressurize the ARB tank and ran like normal. The new compressors have a higher duty cycle and should last even longer. They're better than nothing for tires but i wouldn't rely on it all the time, at least not with frequent use and big tires.
The seal rings in the diff are not an issue anymore, they're good for 100's of thousands of miles.
If you're nervous about switches and solonoids, run manual pneumatic switches. I think the issue ARB stuff is pretty good.
ARB has been around long enough they have lots of time on their designs, lot of upgrades, lots of dealers to get parts if you do need any, lots of people on the trail with experience with them, etc. Time definitely is an advantage in this case and they've been around for a while.
Hope this helps