I285 is often as bad a mess as going through town, but if there is no accident or construction (there is), it can be an option midday. For us, there isn't a "going around" option of course.
The northern stretch of I-285 is really bad, but the western part is probably the best option for getting by Atlanta midday.
For some reason, jamming two 12 lane freeways down to one isn't working well in town (the Connector they call it). We exit just before the connector on 14th street. We go up to Costco north on I-75 and return the same way. I know some alternative routes now if I-75 is jammed.
I-85 outside the perimeter (285) is really bad, it gets better inside until you reach near the Connector at Brookwood interchange. There aren't even PLANS to fix any of this except that northern Arc (there is a plan for that).