Impressive as hell. We did the landing tour, which was pricey but worth it. Whole experience took about 5 hrs. They picked us up in a nice shuttle from our hotel, and then we drove about an hour outside Vegas to Boulder City airport. We had to wait 40min bc of a weather delay (rain inside the canyon) but you can't blame the company for that. There was seating for 6ppl inside the copter, and we paid the extra $50 each to be seated in front (definitely worth it). Captain was extremely friendly and personable.
The flight took us over the Hoover Dam and 3 large basins of water. The captain was extremely knowledgeable about everything: how the copper makes the water appear green, a sunken B52 bomber in the lake, various mines and their history, and just general Grand Canyon info. Then we got to land in the Canyon, where we disembarked for a light lunch and took millions of photos. We spent maybe 30min on the ground before we had to leave again. Each copter leg of the trip took about 45min or so. Whole experience was very pleasant.
I bought the tix from Bill's in Vegas (1/2 off place next to Paris hotel). Although these tours aren't really half off. Spent $365 each + $50 for upfront seating. So $830 for 2ppl (price included a free show at the V Theatre at Planet Hollywood as well). But how often do you see the Grand Canyon?!?!?! Definitely get the helicopter tour.