I've had HiPers for about 4 years now, and wouldn't get rid of them for anything. Front beadlocks - never, ever a problem. Rears - the integrated hubs were discontinued, and HiPer had a good reason - people wouldn't maintain them, axle nuts get loose, hubs strip. HiPer has to send new ones to you for free. In addition to that, it's all about tooling and machining money - to many axle dimensions out there, in diameter and spline count. Doesn't make sense when they can make one bolt-on hub center with dual bolt pattern, and it fits everything. Smart money.
The old (original) style dual pattern centers were discontinued and recalled. I had a set of those, so I called HiPer (I think this was '04 or '05) and they sent me the new centers free. Hell no I didn't put them in - my old ones were fine!

Yeah, a month later, I had my right rear wheel pass me after landing a jump...

New centers went in that night.
If they leak air, they;re not torques right. It's something like 9~11lbs for the rings, and 10~12lbs for the centers, or vice versa. I just keep them all torques to 10lb/ft and forget 'em. For the dual beadlock rears, that 36 bolts each wheel (12 in each ring, and 12 center bolts), and they're 12-point 7/16" bolts. PITA. Worth it, though, once a month? Yep.
Weight. I've weighed out a set of 9" HiPer dual beadlock rears against a set of 8" Douglas Yellow Label single beadlock rears, both mounted with 18" Klaws, and both wheel combos weigh exactly the same. Benefit of the HiPers in that situation? Dual beadlocks and not singles.
I've never flat-spotted a HiPer, and had to beat it out with a deadblow hammer just to keep going. I've never unbeaded a tire with them. After I changed out the centers, I've never had a problem with breaking out a center.
I'll toss up some pics tomorrow of the differences in the old centers and the new centers. It's easy to see how the old ones could break under the right circumstances, and why the new ones are stronger and better. That stuff was fixed at least 3 or 4 years ago, too.
I'd stay away from the ones with the CF centers, though.