Unlikely as it sounds, a company called Fleurville makes a very decent-looking dad-friendly diaper bag, if you choose the right material. (They finally introduced black canvas this month. Yes, they have camo, too.) The Alpha 7 is loaded with the baby-specific functionality found on their other bag, The Mothership. Also, it converts from shoulderstrap to backpack. Sounds heavy.
A good friend gave us Mum's messenger-style diaper bag, and it's pretty solid. A nice combination of function and unfluffy design. Check it out at Pokka Dot.
For 60 years, resourceful WASPs have been hauling any and everything in L.L. Bean Boat & Tote Bags, so why not diapers and bottles? You can get shoulder-length handles, a zip-top, and monogramming. And at only $24, you won't be dipping into principal, for which the kids'll thank you.
Don't call it a diaper bag; it's a a "dad field bag." What it really is is a Jack Spade messenger bag with a changing pad (and a sippy cup in the picture). Of course, you could just buy a changing pad and turn any bag into a diaper bag.
I'd say the LL Bean Diaper Bag (in Black)is also "doable" no?
The bag that is available at Pokka Tots is not available there anymore. But you can buy it at diaperbags.com for $80. Made by a company called Mum.
Another great bag I found (and the only one I use, even though I have 4 others) is the Zip Top Small Tote by Mountainsmith. It has a rubber base, so it is stable when you put it down and interior pockets that are perfect for bottles. I use it with a little changing pad kit from Sammy Design called diaper bag express. Here are links to both items.
[i added them in. -ed.]
My hubby uses a messenger diaper bag by Kecci - they don't look a thing like a diaper bag, but have all of the nifty things needed to sport baby. Great changing pad which velcros to the inside (so as not to get smashed or lost amongst diapers etc.) and lots of pockets to stash keys and phones. You can find it at www.sweetnoelle.com - $34.95.