Potential spoilers for anybody who is thinking of running Storm King's Thunder.
Almost full-day game session two days ago went smashingly well! I decided to make a "battle-royale" style final encounter, and it was scarily epic. Sorry I didn't take any pics, but first of all I broke out my Dwarven Forge castle terrain and built a ruined amphitheatre for the battle ground. Then broke up the encounter into two parts (with no ability to rest in between, just a few round break). Hero side was a party of eight characters (four 10th level and four 8th level) and two storm giants. Part 1 villain side was 30 gargoyles and 1 ancient blue dragon. Part 2 villain side was what was left of the ancient blue dragon, 2 adult blue dragons, 4 enhanced air elementals, and a mummy lord. The parties survived, and except for the storm giants (which weathered the battle pretty well), everybody else was down to their last handfuls of hit points, and just about every magic resource got exhausted. I suspect that without the storm giants' immunity to lightning damage that the battle would have gone much worse.