I've taken US 301 to bypass the DC area. It is a viable alternate, but only if traffic on I-95 through DC is very bad.
US 301 through southern Maryland is not access-controlled, meaning that it's got red lights instead of interchanges. And through a 10-mile section in Anne Arundel and Prince Georges counties, US 301 is very busy, especially on a Saturday afternoon or evening, because it's full of restaurants, shopping plazas, and businesses. It reminds me a little of US 192 through the Maingate area.
However, this past weekend was one of those times when it was well worth taking US 301, because I-95 had major construction delays at the Woodrow Wilson Bridge (4 lanes narrowed to 1 with 2-hour delays).
When traffic on I-95 is moving normally, I-95 is much faster. But when I-95 experiences construction delays, US 301 is faster.