From what I have heard, as of late their service isn't all the best (what do you really expect from Mongolia?), but their aircraft are ok. They currently operate A310s and 727s. I take it you will be flying them from Osaka?
If you can, try and snap a few shots of Ulaan Baatar Airport and post them on here, and let us know how the trip was....would be interested to here, as I am planning on doing a trip to the steppes of the Gobi Desert in a year or two.