The Midsummer Fire Festival should now be live on almost all North American realms. If it isn't, it will be shortly! Not much has changed since last year, beyond the addition of the achievements.
Speaking of achievements, while we have our guide to the Achievements of Midsummer, you might not be able to make a significant dent in them today if you made rounds with the flames last year. None of the quests seem to have reset from last year, so getting your hands on the holiday currency to buy the items you need is going to be difficult, to say the least. By difficult, I may or may not mean borderline impossible.
I don't expect this to be a permanent issue, we'll probably see a hotfix sometime in the near future since the problem is already being checked out. Of course, that's assuming the issue is something that can be hotfixed. If not, I don't doubt we'll see a fix of another flavor down the road. I don't foresee Blizzard keeping What a Long, Strange Trip It's Been out of players' hands because of something like this. In the meantime, at least you can still take a crack at Lord Ahune.