The Borås Arena is a new stadium that was opened in April 2005. I went there for a cupgame in August 2005 and found it to be a great arena. Only had one problem when it started to rain a bit into the stands and then everyone was climbing back and up to higher seats under the roof :).
It is the home of IF Elfsborg who play in the 'allsvenskan' - which is the A league of football in Sweden. The game I went to I saw Elfsborg play Häcken, it wasn't the best game I had ever seen, but was more interesting in the second half than the first and especially when it went into extra time. Elfsborg won in the end 4-3.
Equipment: Hmm... warm clothes, I was there in summer, but probably needed a jumper. And if you're going to support Elfsborg - then something in black and yellow would suite!
Elfsborg is a football club and they have a famous player for the moment when I write this tip (2009) called Anders Svensson. He plays in the Swedish national team and he is an important midfielder both for his team and also for the national team. Elfsborg plays in yellow and blake. The home stadium is Borås Arena, and they dont play at real gras.