I am a huge Tom Bihn fan and I enjoy knitting, so I've been stocking up on my favorite colors when they pop up as Stuff Sacks. I'm using mine purely as yarn bowls, since it can fit both a ball and a full cake in there. It's a big small for a project bag for what I like to work on, but I may give it a whirl for that purpose with my next pair of socks.
The pros: love that transparent bottom so I can see which yarn I've got in there. Plus, it's durable as all get out and comes with that typical Tom Bihn quality.
The meh: The yarn guide is a nice idea, but it keeps tangling my yarn. I think it might be a little too big for its intended purpose, or possibly the problem is the way it sits in the bag. I keep getting into the zone and then realizing I have to stop and untangle my yarn again. This is a problem I've only had with this bag, and I'm still trying to figure out how to make it stop. Also, the new default size is a bit big for my project bag once my project starts getting bigger.
Overall: Happy to have it in my Tom Bihn collection, and hoping to find a way to better integrate it into my favorite hobby one of these days!