I just picked this bag up off of S&C for a steal. Biking around school in Oregon requires that one gets a bag that can keep out the moisture and you could probably spray this with a hose without water seeping through. A few things to note though: the zippered pockets are fairly flat so it makes stashing more than a few things a little awkward, I got the brown/orange model and I have yet to discover this reflective stripe that is mentioned in the description (the orange stripe on the front is just vinyl like the inside), and the top flap isn't super long. I also have a Timbuk2 and so it seemed logical to make some comparisons. With regards to the top flap, there is the hook and loop closure which works amazingly well. However, If you don't pack the bag so that the top opening has the front nearly touching the back, the top flap won't reach too far and won't even cover the D-ring or key hook on the front. The bag isn't padded at all so I use a neoprene sleeve for my laptop (9.5" x 14.75" x 1.25") and that just fits the interior shape of the bag (thickness at the bottom is still fine.
Bottom line is that it is a bombproof bag that will make you slim down your packing habits so the gear you do take with you will stay as dry as you put in in there.