As a commuter from either BHM, MEM, or JAN, all of which are similar to BNA, your biggest issue is weight restriction. I've been #1 on standby with 9 seats open, didn't get on. From what I have been told by several Express jet guys is that the Cleveland shut down was accelerating their retirement of many of the weight restricted RJs. I have seen a little improvement over the past couple of months, meaning that maybe 1 or 2 flights per day out of 5 or 6 do not have weight restrictions going in.
I think the 70 seaters will help, but United dumps all the small crappy RJs in Delta country, AKA the South, so I think we will hold on to them until the bitter end.
As others have said, our commuting policy makes things a little easier if you miss a trip, but doing 4 commutes per month on a RJ every time isn't for everyone. With min 5 per day and FAR 117 , trips that start late and finish early are hard to come by. I am at 17% in base and can barely get those during the week with no redeyes, which now means you are commuting in night before or commuting home night after, which turns your 4 on 3 off to a 5 on 2 off.
Hope that helps.