I've been using the a large Wald basket zip-tied to a front rack on my '88 Hardrock along with a large Rivendell Shopsack as my main commuting tool the last couple weeks. I've found that the system works well for me. The weight isn't all that important as long as I use nice wide handlebars (On One Mary.) Similar set-ups in the past have not worked because with narrower handlebars I didn't have the leverage to control the load easily. When things got out of kilter, bikes got squirrely pretty quick. I never lost control of the bike but having the additional leverage of the wide bars offers greater control.
That said, I wouldn't want to try a basket connected to the bars. Any steering motion with the bars would move the weight and change center of mass of the bike. Additionally the height of the weight, even by 6 or 8 inches can exaggerate any movement. Putting the weight lower is generally better, so I find.
There's a picture of my set-up in the Commuter Bike thread if you're interested.