In more than one place I've seen a munter/mule combined with a prussic as the ratchet point in a pulley system, especially in one of my favorite books:
http://www.amazon.com/Glacier-Mountaine ... 0762748621

It's hard to make out if that red cord is actually tied as a munter on the end but I think this is an example is here:

http://www.summitpost.org/ratchet-syste ... ing/700714

But even the Glacier mountaineering book shows multiple OTHER illustrations of just a simple prussic or even an auto block with no munter/mule.

My question is, is the adjust-ability worth it over a prussic on a simple loop? Creating the prussic hitch is a PITA when you've got 8 ft of rope hanging out the other end and it just takes that much more time while somebody might be dangling in an icy crack. If you do need to back it down, can't you just have your third mind your prussic and let it slip as the hauler back-peddles?

Funny, I was just going over this same exact thing after reading through that book. One of my favorites also.

First, from what I gather I'd say the main purpose of having the munter-mule is to easily transfer the load from the prusik to a belay in the event that the fallen climber is able to be lowered and walk out of the crevasse. Otherwise, if you have a simple prusik loop, you'll have to do some hauling to get it unloaded before you can lower the climber. Maybe you do it by hauling on the 1:1 if you have enough people, but most likely you'll have to set up a quick Z to unload the prusik and then lower the climber.

I would not say the purpose of the munter-mule is to back down an already established hauling system. In that case you can have someone mind the prusik while the haulers back it down...like you said.

Now, given that, here's my take on using it or not:

Mostly all of my glacier traveling has been on a two-man rope team, so we've always just had our short prusik loop (doubles as your chest prusik) rigged on the rope ready for a rescue. In the event of a fall and the person outside the crack is able to arrest, he must set the anchor quickly all while holding up his partner. In this case I feel clipping the simple prusik loop into the anchor is going to be a lot easier and less stressful than trying to rig a munter-mule to the anchor mainly because you want to get yourself unloaded as quickly as possible. I mean it wouldn't take much more effort to have munter-mule rigged up and ready to go...but to me a simple prusik loop is just cleaner when it's rigged up while you're traveling.

My partner and I are taking two beginners up Rainier this summer so I've been practicing a lot more and reading up techniques that apply to larger rope teams. That's when I ran across the munter-mule tie off that you are talking about. Since you'll have other climbers holding the fallen climber when you are setting up the anchor, you'll be a bit less stressed to get the anchor set up so a munter-mule won't be as challenging. That being said, the only reason I see to use it is to easily transfer the load off the prusik and back onto someone set up to belay. I wouldn't use it lower the fallen climber any significant distance because, like you said, the munter-mule prusik would have to be pretty long which makes it a pain to set up. I'd make it just long enough to tie the prusik and munter-mule without having much tail. That will be enough to lower a foot or so, enough to put the load on a belay.

So, I will definitely be practicing both methods, but I like the munter-mule due to the fact you can easily lower the climber if needed. But I'll definitely practice lowering the climber with a simple prusik loop. Unloading the prusik and getting the rope on belay might be a little tricky, especially with one person...the better option might be set up a quick Z and then slowly inch-worm them down.

On another note, one thing I really liked seeing in that book was setting up a second anchor using using a munter-mule. A lot of books (including FOTH) and videos show setting up a second anchor with a fixed runner length, which means you have the get your anchor set up in just the right spot...and even then the second anchor might not be loaded at all. By connecting the second anchor to the first anchor with a cord and a munter-mule, it allows you to have a less precise anchoring location and then you can take up any slack with the munter-mule.

EDIT. I was just thinking about setting up a prusik that has a long tail on it for your munter-mule. Another option is to tie in your normal prusik loop and then girth hitch another cord to it that you can then use as your munter-mule. Your prusik might be a little long for your ratchet now, but at least you won't loose the ability to transfer to belay if you need to lower the climber. I dunno, it might take just as long and now you have to deal with two different cords, but it was just a thought.

Yip just don't forget if it is you down the hole to put your ice screw into the wall if you can so that you can unload the rope a bit to help your team if they are struggling to make an anchor and also to save you if something fails. I had and anchor fail while I was down a hole once and it wasn't fun. It creates a heap of load hauling people up, and in soft snow it is really much harder than you think to set up a good anchor by your self if you are in a team of two.