Went there in 2001 with my Dad and a small crew. IMO its the most fun I ever had in Scouts. I had a great troop and we did lots of hiking and camping but Northern Tier was the pinnacle of my Scouting experience. My Dad liked it so much he went back with my brother two years later. We did about 70 miles in 9 days, our longest portage was 1.5 miles, with most of them being less than a mile.
The typical BSA stuff is heavy but works. None of us had the slightest clue what lightweight gear was but we all survived and had the time of our lives. By the time my Dad went I had learned a little about UL hiking and I made a number of clothing suggestions that they appreciated. Namely, synthetic clothing which dried quickly. You'll spend most of your time being damp. The thing that could have used the biggest overhaul when I went was the food. Suffice it to say we had way more cookpots, pans, and stoves that we ended up using. I'm not sure what the standard kit it now but I'll bet its still overkill.
Rain gear was a must when we were up there, we got two straight days of rain, one so bad we sat most of it out at the campsite. Bugs were bad every night. Long sleeves, long pants, and a headnet are highly recommended, as is being in the tent before it gets dark. If the BSA still recommends jungle boots I would say they are overkill for 80% of the portages we did, but the quick drying aspect is nice. I think I could have got by with a sturdy pair of trail runners and been much more comfortable in camp. I wore swim trunks during the day, which was a good choice and then wore a pair of rain pants over them in the evenings when the bugs were getting bad. If you have a favorite PFD, bring it because the BSA's were a little skanky when I was there.
Some highlights for me were eating walleye we caught during the day, Yum-Yum (a particularly wicked portage, which Sigurd Olson mentions in one of his books), a campsite with a crude log picnic table that wasn't supposed to be there, seeing a bald eagle (unheard of in my home at the time), losing two of our three methods of water purifications by the second day, white caps rolling over the front of the canoe on a particularly windy day, The Yellow Brick road (a pretty easy portage), and the B and the B (Bit** and Bast***, two very tough portages in very close proximity).
I want to go back very badly, though not necessarily with the BSA. Its absolutely beautiful and one of my fondest memories. I wish that I had brought a real camera along. Specific memories have faded and I wish I had photos to remind me. My Dad and brother took a camera when they went and they I love their pictures. I chose to do Northern Tier instead of Philmont and never once regretted it after hearing about other Scouts' experiences. Not the Philmont sounded bad, but Northern Tier is less about the activities and side trips at the campsite and more about the journey from camp to camp. We were often too tired to do much more than cook dinner, soak in the water for a bit, and hang the bear bags.
I hope that you make as many memories as we did, no matter what gear you decide to bring.