I went through this as a player first, then later I DMed it (both in 2e). As a player I enjoyed the variety of quests necessary to locate the mountain and get the pieces of the amulet. I was really, really impatient to reach the mountain itself, certain that it would be a monstrously cool dungeon that would totally roxxor my soxxors. The DM flubbed some of the rules, allowing the party to maraud about the place ethereally and avoid many of the killer traps. He used the kobolds pretty well, though, including a whole bunch who had strapped flasks of greek fire to their bodies and would charge us madly like diminutive suicide bombers, blowing themselves up in gory sacrifice.
He had replaced the standard dragon with some twinked-out monstrosity of his own making - a kind of evil avatar-dragon that had captured Elminster and was draining his life-force (yeah, it was an FR game where we had to rescue Elminster, heh heh). We had a completely insane battle against the dragon (during which Elminster was killed and turned to ash in my arms, oh happy, happy day!). In the middle of the battle, our wizard's faerie dragon familiar suddenly turned out to be a gold dragon in disguise (wtf?) and joined in the battle with us. We killed the avatar-dragon with her help. Then Bhaal (FR death god) turned up and killed us all with a wave of his hand. Then the gold dragon turned out to be an avatar as well, and banished Bhaal and returned us all to life with a wave of her hand. I suspect that the DM got carried away at some point during the final battle, but I'm not quite able to put my finger on the exact moment....
When I ran it as part of my homebrew, all the dragons of the world were dying and Dragon Mountain was their only hope of escaping their doomed planet. I changed many of the initial quests to suit my own game and had the mountain beseiged by a number of dragon and dracolich-led armies. As for the mountain itself, I added a bunch more dragons, making them the brood of the mountain's uberdragon, each with their own lesser broods and factions of dragon-humanoids beneath them (I removed the kobolds completely and replaced them with the dragonmen as I thought that kobolds were lame for a 15th-level game). I also added a City On The Mountain, established on the slopes of the mountain by those who accompanied it on its planar travels, but were never allowed entry into the mountain itself - a parasitic society of planar dreck and "pilot-fish". We played about a dozen sessions in all, very enjoyably, in a combination of religious/political intrigue and kick-ass battles against invading armies, indigenous dragons and factions of dragonmen. I had this whole plot about the dragonmen seeking to liberate themselves from the harsh rule of their dragon overlords, and various broods of dragons struggling to take the place of the ailing uberdragon. The plane-shifting mountain remains a part of my campaign, now occupying a central place in the gameworld's mythology.
In essence, I agree with those who have said that the adventure doesn't run very well as written. I had lots of cool expectations about what it would be like, and very few of them were realised. So when it came to running it myself I replaced all the bits I didn't like with those realised expectations and me and my players were satisfied with the outcome. As written, I think it's a missed opportunity for draconic coolness. Instead you get a pale imitation of Tucker's Kobolds and one rather dim dragon. My final version was so heavily reworked that it might as well have been a different product. A real could-have-been product that should have been something else.