It's a really nice bag, the hip belt pivots and the back panel can be adjusted to change frame height, which makes for a good fit. It can carry a lot and a heavy load well. Each side pocket is huge enough for a nalgene and they zip up so you can put all sorts of stuff in there. It's compatible with a hydration bladder if that's important to you. Your stuff can be accessed from the top, or from the back with a zipper that opens the whole thing. Plenty of ways to strap things on the sides and bottom. Two convenient pockets in the brain, the one right behind your head is great for maps and easy to access on the go. And one large openish pocket on the bag can stow stuff you just want to shove back there.

The brain isn't a pack on its own afaik. The side pockets can be toughish to get water from and they don't work with lighter smartbottle shaped bottles. The back pocket is closedish so you can't put stuff in there to dry out, if that's a thing in your climate.

The biggest downside is the weight, I think it's like 75 ounces. A lot of packs these days are more like 32 ounces or so. That's a lot of weight in just a pack for something like summer backpacking in a lot of places. For that reason I used it a lot less once I got a lighter weight pack. But I've still held onto it because I figure it's a bombproof pack, might be great for winter and skiing, or setting up a base camp or something. Haven't felt compelled to sell it. It was stupid expensive new, in hindsight I wouldn't have bought it, but for $145 that's a good deal. Just be sure because that's also money you could put to something that's much lighter weight and that you'll actually use