Yes, backpacks still raise an eyebrow in some types of meeting, sadly. But as more people cycle or run into work that is changing IMO. If it matters to you or your clients, go for a double-zip briefcase/bag with shoulder strap and a laptop cell that provides the extra room you need for your stuff. Personally I'm not convinced by a backpack unless there's some serious distance to be covered on foot while carrying or lugging another bag. In normal stop-start air travel mode, it always seems to be on my back when I need to access something quickly, or I'm slinging it as a shoulder bag which rather defeats the point.