I'm liking my Timbuk2. After half-a-year of hard daily use it's almost as new. The only difference I can discern is the addition of sweat stains and I'm certain that's my fault. The fabric, the stitching, etc... all look unworn at this point. Being a bit of a connoisseur of working backpacks it's wearing in about how I'd expect one of my $300 work packs to. That is I expect it to last decades with minor repairs. My only complaint is that the main chest strap could be wider. I wouldn't describe it as narrow but wider would be nice for heavy loads. That change would worsen ventilation and sweating though. If you're interested in a Timbuk2, keep an eye on their website. They routinely do 50% off deals on a lot of their products there.

Another option and I think a better one for what you want is a bento bag. It's a small bag that mounts to your frame and stem. I know Jand makes a popular one that I see in bike shops. Similar carrying capacity to a saddlebag so if you're saddlebag is full of tools and spare tubes the bento bag can take your keys, wallet, phone, and snacks. It won't fit a u-lock though. The main advantages of bento bags is that they're cheap ($5-10), don't cause sweating like backpacks, and the stuff is easily accessible while you're riding. And a bento bag would complement your big messenger bag by giving you a place to store pocket items rather than constantly loading and unloading them from the backpack.