I drove the entire length of the Coalfields Expressway yesterday heading westbound. Starting from WV 16, WV 121 is now signed as the route to Mullens. WV 54 is now signed for Lester (I think). WV 121 now has two through lanes, leading to the west/south direction of Robert C. Byrd Drive being four lanes wide near the WV 16/WV 121 split.
I didn't observe any changes in the section over to Slab Fork Road that has been open for years.
Past Slab Fork Road, the road and shoulders are concrete all the way over to Mullens. Traffic was light - this could have been built as 2 lanes without any real problem. There were I think three places where there were "intersections" with access roads for adjoining properties, but there are no connections to other public roads in the 9-mile span until you get to the Mullens connector. The road was not built on top of the ridge as I had expected, but rather about halfway up the side of the ridge. There are a number of large rock cuts and some decent fills.
As you approach the end of the new section, the speed limit drops to 55 and then to 40. It ends in a 90-degree turn onto the Mullens Connector, which is signed as "To WV 54" and "To WV 121" rather than WV 121 proper. WVDOH did not build any stub of the mainlane past the interchange, so any future construction to extend the road will impact the mainline. The road basically ends in the side of the mountain, so a lot of earthwork is going to be required for an extension.
Heading into Mullens, the new connector is two undivided lanes (no climbing lane) and is quite twisty. It is signed for a mile-long 11% grade. I hate to see what this will be like in the winter. I suspect a lot of people will stick to WV 54 during bad weather.
The new road improves connectivity to Mullens, but I'm not sure how useful it is beyond that at this point. WV 97 is/was the preferred route from Pineville and beyond to Beckley because of its better alignment over WV 16 west/south of Mullens. I don't know that the new route really changes the arithmetic. WV 54 is already a relatively modern road between Mullens and Beckley. I think WVDOH would have been better off focusing its efforts west of Mullens or perhaps south/west of Pineville, where the new road would have represented more of an improvement over the existing network.