We carried quite a lot of gear on our JMT hike. Despite aiming for lightness, we really felt that our knees and other joints would have been much happier with a lighter load. We felt that we were not being slowed by muscle fatigue, but more by sore and tired feet, ankles and knees. That said, we have, and will continue to, use much of this gear for winter camping or situations where ultralight gear is unsuitable or unsafe. Our gear list can be found here.
One of the best items we had was a sweet tarptent, the Tarptent by Henry Shires. We absolutely loved it. The other item we had with us, which was worth its weight in gold: mosquito headnets. We were hiking when there was still plenty of water in the high Sierras, which meant beautiful wildflowers, but also tons and tons and tons of mosquitos. So bad that Lis almost quit hiking because she couldn't stand them. Luckily the headnets and full rain gear (plus a shower of DEET) prevented us from getting off the trail.