How often do you use the 3rd ring? I have 3 rings myself and I rarely use more than one, so if I wanted to do it I can't see where it'd be a problem? Are you wanting to put a bash guard on the 3rd ring?

I do more road biking than mountain biking, but I had a 3 ring road bike and then bought a new road like which was 2 rings. There are many times I have regreted losing the granny gears. I feeling is unless you are an avid rider in super shape I would not give up the granny gears, especially on a mountain bike where top speed in not the primary concern but climbing is.

I'm more of a roadie. I did, however, make the conversion for 3 ring to 2 ring. I went with a compact though and, have an extremely wide range on my cassette.

2 ring conversion can be good if you keep in mind the range of gearing. You can still have the same low granny gear, and still the same high fast gear. What you would find as there would be larger gaps between the gears (not physical gaps, but exertion gaps).

So on my old road bike I have a triple 50/39/30 with a 10-spd cassette 12-27. My new bike (which I built and I love it) has a 2 ring compact. 50/34 with a 10-spd cassette 12-32. So I have the same top speed 50 to the 12 and in essence the same slow speed 34 to the 32.

You're probably running something like a 22/34/44 in the front, right? If you were to simply drop 1, then yes, you'd lose a lot of gearing. But if you went to something like a 24/38 you wouldn't loose too much off either end. You may well find yourself jumping between the two more than you do with 3 rings, but you shouldn't lose much noticable gearing for 90% of your riding.

I ran a 22/34/bash for a long time, then got a race bike with a 24/38 and noticed virtually no difference.

Also, you may well have to change out your front shifter if you go to a double. Some people can get away with using the limiting screws, some people can't.