I'll be switching to a set of front runners...tho might be staying 15". My advice for any of you; unless you NEED the extra reduction in resistance, or have a REALLY light truck, do NOT go with a 3" front runner (either the 3, 3.5 or crazy 1.5). They can't handle the front-loaded-ness of these trucks, nor do they provide quite as much breaking force (and you need every bit on a light rear ended truck).
My camp has been rolling mostly 4-4.5" front runners, and the difference is huge. We have routinely used them on the street as well, a very nice bonus for any of you grudge racers and no-prep/no-trailer winners
The downside being that not every rim style/pattern is available in every section width, and your always limited on tires.
Thats my .02 as someone who does mostly street/street performance/grudge stuff, but still likes the look and the benefit for track use.