I have been twice, great time especially if you like three continuous days of celebrating. You need to be invited into a Hall to see the Guizers performances though, not really a tourist thing as you can't buy your way in, just a personal invite from the Hall's host. If you want to go next year you need to book a hotel now as they soon fill up as many expats return for the week.
The Guizer Jarl leading the Jarl squad is elected for a year and becomes the face of Shetland, touring the world and leading the community, a bit like a mayor. A very important person there, with a lot of influence.
A key document is "The Bill" which is worth trying to read but is fairly impenetrable to non Shetlanders. It sums up the year and covers politics, in-jokes and pokes fun at officialdom.
It is not a re-enactment in any sense but a Shetland cultural celebration. They appear to regard themselves as separate from the UK and aligned but not of Scandinavia. There is defiantly a different mind set there. I would love to move there, I love the place.
In 2012 how many God-fearing, tax-paying, law-abiding men in Lerwick were there in the Up-Helly-Aa parade?
Both of them.