Once you figure out how to use this, it's so simple and easy and it's everything built into one. I'd been using thin runners to clip in the anchors during hanging belays for multipitches and as much as I trust those things for everything else and know they're amazing, my mind would always look at them and think they looked like old shoelaces. Then there was the rearranging of gear or hands to rappel or belay…etc. This seems like it lets you do all those things on one piece and minimizes the unclipping or tying or whatever you have to do. One less thing for me to remember to do or double check is welcome. Plus it has the added bonus of seeing a big sturdy blue thing holding me on when I cleaned the anchors for the first time and untied myself from the rope. Piece of mind when climbing goes a long way.

With it girth hitched into my harness its a little bulky because of the thickness, and you still need a 2nd one if you want to be redundant. I have used it once to clean and don't like it, but for top belaying it works. It doesn't cost much and a good rack is one with options so no regrets.

This thing is great! I use it to anchor for sport, trad and ice as well as rappel. It works so smoothly. On top of that you can belay a second off of the belay loop section and back-up your personal anchor with a couple clove hitches. This is only really necessary when there is a nasty belay setup.

I really like this, use it sport and multipitch trad. I stays out of the way until I need it, gives me a quick connection to the anchor and all, but I really like rappelling with the rap device on the center loop, Petzl reccomends this belay method but using a regular runner, this is better! I am 6' tall and have both lengths, the long one is too long for my tastes, it reaches to the limit of my arms length, putting the anchor pretty far off. I will be using the shorter one most of the time. The long one will be for belay stances where I want some freedom of movement. Get one, it's great.

I've been using this for sport climbing a lot and it simply makes things easier. Use it as described in Climb2love's answer below. The small loop in the middle is brilliant for abseiling off instead of using the central loop on your harness. I'm a tall guy (6,5) and use the 90cm. Great length that fit my range. Smaller guy's anf girls might consider using the shorter one.