I just received the Shift this weekend and played my first round with it yesterday.
1) I agree that the internal pouches on the inside are virtually useless. Also, I am not sure where to stick the cover while playing. Do I roll it up and stuff inside?
2) The first time using it the discs were rather snug in their sleeves, but I bet with more usuage they will hold in there just fine.
3) The side pouches in the waist strap are just barely big enough to hold a wallet, phone, or keys. So, it works best if you put stuff in there that you will not need to have out during the round.
4) The back pouch where it is advertised that you can hold your drink, it can only hold skinny drinks. The Gatoraides I normally carry are too big for that pouch and I would be forced to carry them inside in the main compartment. Not a big deal, but anything that becomes stuffed inside could interfere with retrieving discs from the bottom-most pouch.
5) There is a lot of cushion against your back, but it is not in the least bit uncomfortable.
6) Having the pockets on the outside to carry your four most used discs outweighs any negatives associated with getting at discs on the inside. Right now on the outside I have an Ion, Tangent, TeeBird, and Leopard.
As whole, though, it looks rather well constructed it and it is very light (I was not carrying any liquid refreshments with me at the time). Because it only carries 12 discs, I still will not use it for important tournament rounds, but worked well and was not cumbersome for a normal rec or league round. It is essentially replacing my Crunch bag, which also held 12 discs.
The Crunch was more convenient as I could get at discs quicker and or could just pick up the bag and go. Yet as a way to carry your discs and other items, the Shift has the advantage because it is a backpack, that it sits more cleanly against your back, and therefore is less cumbersome. If I am carrying my bag and I need to duck, move quickly, or carry something else, having it strap firmly against you means a lower probability of discs falling out, the bag shifting on you, or just becoming too much of a burden to one side of your body.
I am liking my Shift so far.