How formal does your "everything" bag need to be? I use a Baggallini Avenue Tote as one of my everyday work bags. It fits my 13" laptop (has built in padded pocket), but also is a useful personal item when I'm traveling somewhere by plane. (I especially like the back pocket that unzips to slide over my suitcase handle.) It's lightweight and nylon, but possibly too casual for some folks. It holds a good amount without completely overwhelming my petite frame. It's also nice to have the option of using shoulder straps OR the crossbody strap.
For somewhat more formal occasions, I have a Knomo Little Portland tote, which also has a laptop pocket. It's less flexible as far as hauling around a lot of stuff, as it's a lot slimmer. So I don't like using it when I'm schlepping around, say, a lunch along with my laptop and work portfolio. But it's a bit less casual, and sometimes I want that.
I generally don't bring my laptop to really formal occasions, like interviews. I suppose I could put my laptop in its sleeve in my Dooney & Bourke tote, but it wouldn't be comfortable. Even the lightest laptop gets heavy awfully fast if you're carrying it around all day in the heavy leather bag with shoulder straps designed more for looks than function.
