I will most likely be staying near BWI and heading to the Inner Harbor area (via the Key/I-95 tunnel) on a Wednesday AM, and heading backto BWI in the early evening.
Does anyone have an idea how good or bad traffic is around this time, and how much to allow?

I'm not certain where you are going, but most of inner harbor is accessable before going through a tunnel from BWI.

Traffic usually is not bad at all. Not like DC, NYC, or Atlanta.

30 min. gets you most everywhere from one end of the interstate to/from BWI. Same cannot be said for the beltway, which frequently hangs up badly.

It is easy to get lost in downtown, trying to escape to I95. The lightrail goes to downtown from BWI.