Sterling Chain Reactor Canyon Sling - 2010 BCS

It is identical to the Metolius in function, but it does not come with the Metolius locker (which isn't a great biner, you probably don't want it anyway), and is made of 100% Nylon as opposed to the PAS Nylon Dyneema blend.

I would, however, question the actual value of both of these items that are so bulky, expensive, and unnecessary.

At a multipitch belay, the rope and a clove hitched locker do a much better job of anchoring you in, keeping the dynamicism in the system and giving you even more adjustability . For cleaning sport climbs, I just lock directly to the masterpoint of my existing redundant anchor, then set up the rappel. Extending rappels can be done easily with a light $4 sling, which is also good at a lot of other things.

The only real use I can think of for this piece of equipment is efficiency during temporary anchoring to bolts while doing consecutive rappels. (note that even this could even be achieved with a higher margin of safety with two single slings girth hitched to the hardpoints of the harness). The problem is that if you are doing a climb with consecutive rappels, its tall enough that you'd do everything in your power to minimize the crap on your harness, and this doesn't have the functionality to weight ratio to make the cut.

They're virtually identical. The Metolius ones are a bit stiffer because they have more bar tacking, so it might be easier to clip into with one hand, but otherwise they're the same thing.

Girth hitching something like this (cloth to cloth) is fine as long as you're only loading it with a body weight load, which you should be doing with this. The stresses it will be seeing from a body weight only load are not high enough to cause the stress concentrated areas to fail. Now catching a lead fall...that's a different story.

Most people go ahead and Girth hitch them. You are true that normally you dont want to girth hitch two fabrics together it does weaken the system but you shouldnt be falling on this system anyways. Also if something it girth hitched to your harness for to long you could wear out your belay loop (what might have happened to Skinner), it should be fine unless its always really tight and for a long period of time just be sure to inspect your equipment and you will be fine.

I use a Metolius PAS which I hitch to my belay loop, it works great! The hitch should really only pinch the sling if you take an actual fall, one aproaching factor 1 or higher. This product is desinged to eliminate that by allowing you to choose the right length for the anchor without the unzipping problem of a daisy chain.

And its super useful for situations like leading in blocks, parties of 3, any situation where making an anchor out of the rope doesn't work so well. Also great for clipping into rappels.
I've tried the purcell prusik and didn't like it. The adjustability wasn't as good, it can slip occasionally, and is actually more difficult to adjust.

The idea is to avoid the daisy chain problem (see http://www.youtube.com/watch?v=Be17lI-rVyU). And for that it works well - all the loops are full strength, unlike a daisy chain.

That said, it's still a static anchor connection, which is dangerous. If you get hit by rockfall or are precariously balanced above your anchor, this is not particularly safe. I highly recommend you look into tying yourself a Prussel Prusik, which is both more useful and safer.

You can use this daisy chain like you would a regular old sling to tie into an anchor station or belay. This just gives you different lengths to choose to clip into opposed to just one on say a 60cm sling.