I've been to every incarnation of this location since 2000, and this is the very best one.
I love the Frequency and to be completely honest Madison-dwellers should too. There are a limited amount of small venues in this city for local and small acts to play in an intimate setting. Additionally, in Madison there are a limited amount of venues that charge consistently reasonable covers for said acts. The Frequency fulfills these needs and so much more. The beer selection is quite large. The staff has always been awesome.
I greatly appreciate their policy of not charging a cover if you simply want to sit at the bar and hear the bands wafting through the club. (Although there are exceptions to this on nights when bigger acts play, but they're pretty polite about it, so there.)