DISCLAIMER - I've never worked with vinyl before, and I had a little bit of trouble when the feed dogs (the teeth that pull the fabric through the machine so it doesn't just sew in the same spot) on my trusty Kenmore failed to acknowledge the existence of the slippery stuff. I had to pull it through manually, and every now and then it would JERK ahead. But I was succesful in that it's big enough to hold my knitting, I can see into the bottom of the bag in order to retrieve lost notions, it's waterproof, and there's NO denying it is a bag. Added bonuses: 1) The pockets (I put one on the inside and one on the outside) are the PERFECT size to hold my knitting diary. 2)It won't look weird if I haul a huge bag into work - I never take big knitting projects in to work on during breaks 'cos I'm afraid they'll think I'm smuggling out 12 dozen eggs a day or something.
So I realize this isn't the best looking thing ever, it's really functional. I wish i had enough vinyl to make a raincoat!