Fantastic tour company and an amazing experience.
I recently visited Reykjavik and booked the Northern Lights Hunt tour with Arctic Adventures. Our tour included caving, a lobster dinner and a super jeep hunt for the Northern Lights. The cave tour was excellent, our guide was very friendly and informative, and the lobster dinner was sooooo good. I'd recommend doing this instead of a bus tour, you get far more out of it from a small guided tour than a big commercial bus tour, and the experience is more personal and unique.
We did see the Northern Lights and they truly were spectacular - a sight I'll treasure for the rest of my life.
Some tips before you go to Iceland to hunt the Northern Lights;
They are never guaranteed, no matter how good the conditions! The night we had the tour was clear, dark skies and the activity level was moderate, but we never saw them until around 3-4 hours into our tour! You really need to look hard for activity sometimes but that's really all part of the fun, and if you do catch a glimpse of activity, watch closely and you might see a spectacular show begin in front of your eyes!
I'd definitely recommend booking with Arctic Adventures, and the northern lights hunt tour they offer ensures a memorable experience even if you don't see the lights! Our guide (Fannar or Freyr I think!) was excellent and genuinely wanted us to see the Northern Lights - cannot praise him high enough!