I use a backpack as my work bag and I'm fed up of how inaccessible everything is (it's got buckle straps, and I have to take thing entirely off my back to get something, e.g, keys, train ticket, etc). Was thinking a 'tote' or 'shopper' type bag would be better - I need something big enough to get my laptop in, and all the other crap... But do they actually stay on your shoulder? Or are they always slipping off?