as Brian mentioned it's generally at-its-best when working wide-open sites where targets are more sparse and spread out.
I have only used mine maybe a half-dozen times, often to re-work a couple of those types of placers I have already hunted just to check them again. A very sensitive coil, and I found it to balance much better on the Impact. The larger coil for the Racer series, original or '2', gets to be a bit uncomfortable in a short period of time. Matter-of-fact, with the Racer 2 I can hunt with the small 'OOR' or round 5" DD coils 'comfortably,' where the 5½X10 mid-sized DD and standard 7X11 get me tuckered out.
When I want to use a mid-sized or larger coil, either the FORS CoRe or Relic devices have served me quite well and are far more comfortable to use than the Racer series. At least for me and my bad back. The Impact, using similar-sized coils, is more comfortable and less fatiguing than the Racer's and almost as pleasant as the FORS series models. It is naturally going to be a little heavier and balance different from the stock 7X11, but I actually prefer it on the Impact when conditions allow me to opt for anything bigger than the 5", 4X7½, 5X9½ DD's or 7" Concentric coils [size=small](all of which I need to replace, except for the 5X9½ and large coils, after the theft from my vehicle a week ago)[/size]. All my accessory coils, 5 detectors and other accessories almost wiped me out when I made an emergent run to the hospital in Portland, OR when my Mom had a serious heart attack. Almost gave me one!
If you have big sites, open sites and are shopping, put it on your list.
Monte