I have used this pack on one trip last winter in Australia, I used it with the 50 litre dry bag and the 2 aluminium stays for a complete weight of 1100 gms. What attracted me to this pack were two things, one it is made by ULA in Utah, a well respected pack maker and the dry bag would enable it to be carried in wet conditions without the need for a liner. In both aspect I was not disappointed. It did rain on the Prom during my visit and everything inside my pack was dry. Other aspects which I came to appreciate were the excellent hip belt pockets, the comfort of the carry, I had about 12 kg when loaded. The usefulness of the front pocket, the ability to compress the dry sack and let the air out at the bottom, thereby reducing the volume.
There is however, an art to pack this pack, the obvious is to treat it the same as a normal pack and load from the top with the pack sitting vertically, because of its design I found this method not very successful, instead I laid it on it frame and filled it that way with light items at the bottom and heavier items in the middle and so on. This was much more effective.
I personally would like to have some more outside pockets so I am looking at adding side pockets, which I think will also add some sideways stability to the pack when loading it.
This is a specialist pack and I will only use it when I am expecting a wet trip or when I am going to damp environments, such as Lapland.