It's also pretty dire if you want to cycle there. Coming from the East, my experience is of having to navigate that awful roundabout that surrounds the imax, then go a short way down York Road (which is not cycle-friendly) until you stumble upon the shared cycle/foot way up Cab Road - which is much too narrow to accommodate the cyclists and pedestrians. Then there are vastly insufficient bike racks for the demand. If the plan can sort those kinds of issues out, I'll be very happy.
Also - not directly related to the station but seems to be within the scope of the plan: Trying to get to Waterloo Bridge from the East is also a nightmare on a bike - requiring either navigating that roundabout, or making a (hard-to-find and unintuitive) detour along Cornwall Road and Upper Ground.
Yeah, Waterloo East badly needs some kind of concourse. I guess to be most useful to passengers who actually are exiting (as opposed to getting another train from Waterloo) it would be better for the concourse to be at street level - and so, below rather than above the tracks.
The absolute ideal would be to just rebuild the platforms further West, so the station can really become a part of Waterloo, but that would be expensive and I'm pretty sure is not in the plans.
I tend to use the main concourse if waiting for a train from East. It's got all the necessary facilities.