I sharpen 20-30 loops tof RDR each month for a couple of large fire departments. They use it as it is designed to be used- for roof venting. I've tried it on my 066 just for grins twice- the FIRST and LAST times. It really does cut about like a dull semi-chisel chain in regular wood. In dirty (skidded out) or frozed wood, it may be OK, but not much better than OK.
If you're venting an attic- cutting through shingles, felt paper, plywood, joists, nails, and teco plates. It ROCKS at its intended purpose. For general cutting, not so much. I've used the Rapco chain and it hammers through wood like a stump grinder, it doesn't "cut" like regular chain.
I'm about the only guy in the DC area that repairs and sharpens carbide chains. Our local fire department sidelines an RDR loop if it has 3 or more damaged cutters. I punch these out and rivet in new/used cutters. The big safety issue with RDR is that folks don't carefully inspect it after each use. Pay particular attention to any broken teeth- the hazard isn't a missing cutter, but the often-seen damage to the rear cutter rivet joint when a cutter is broken off by hitting a solid object. A compromised rivet joint is a catstrophe waiting to happen. Be sure to clean and inspect these chains carefully prior to sharpening. I often use cutters that have been salvaged from RDR's that are too damaged to repair. This is a cost-effective way of returning a chain to service. No department has ever complained about me using cutters salvaged from surveyed chains to keep other loops in service.
When you consider that these RDR 20" loops are $240-ish, it makes good sense to repair them. This isn't your average chain sharpening job- charge accordingly. That diamond wheel for my Stihl USG sharpener was about $300, but it has done HUNDREDS of RDR's over the years. It was a serious investment, but I'm glad that I spent the time and money to develop this niche service. I love seeing a 5 gallon bucket of RDR loops waiting for me. It really is money in the bank.