I used the new platform for the first time today, and I was impressed by it. They seem to have put a lot of thought into the permeability of the platform, and having all of those connections will do so much to relieve congestion. The ceiling does seem low, but the platform is so well lit that it doesn't feel cramped at all. It also looked like they'd made some progress on the edge of the old platform. There was a sheetrock wall in one spot, and there were other areas where the protective edging had been removed and the underside of the platform reinforced. The new is already a huge improvement on the old, even in its unfinished state. By the end of the year the entire experience of going through Union will be way more pleasant.
The one thing I couldn't figure out though was the western-most set of stairs to the new platform. The interior of the stairwell has a different finish, and the stairwell also looks like it was set up to allow for it to be closed off. The hallway at the top of the stairs also passes by mechanical rooms for the station (with windows in the doors to let people see into the mech rooms?) so I'm wondering if that access is eventually intended to function as a back-of-house area?