Okay, I finally made it down there this afternoon for a wander around (at least of the bits outside the ticket barriers - you can no longer bypass them by using the lifts).
Entered via the drop-off area ramp on Hill Street. This seems like reasonably functional car access for the purpose, with plenty of disabled bays. There's also a short-stay car park that I didn't explore. The signs lead you through a plasterboard tunnel and a set of fire doors to the main station foyer.
The Initial impression is that it's clean and grey, indirectly lit in a way that seems both bright and dim simultaneously. I saw two wireless (they had big aerials hanging out the back) cash machines immediately next to the entrance (barakta had trouble finding one last week). There's a left luggage, a Network Rail reception desk, a proto-Starbucks and a nice big set of departure screens as per the previous incarnation. A bit further down is the new ticket area (several desks and an abundance of machines, and another 6 cash machines), then a big confusing central atrium area with paths heading in all four directions (left to the new platform access area, right to the old one), and escalators leading upwards to the Pallasades. I can see how PB and barakta had trouble here - all you can really see at this point is grey, crowds and the prominent shopfronts of Boots and WHSmith. A conspicuous lack of signage just where you need it, and plenty of people changing direction and standing around looking confused.
As I didn't have a ticket, I carried on towards the new entrance on Stephenson street. This leads up a gentle slope, with signs pointing to 'Moor Street and Buses'. There were a couple more ticket machines this side, but no ATMs. At the top of the slope, a set of shopping-centre-style doors lead onto Stephenson Street, with the walkway (more in a minute) on the right. I turned left here, and walked past a long row of closed doors to the new entrance area. This was light and airy, and contained ...some stairs to the car park. Exiting onto Stephenson Street, I retraced my path on the outside of the building, through what I correctly anticipated to be a crowd of loitering smokers. It has a murky 'bus station' feel to it, but no actual bus stops.
Signs pointed to Moor Street station, along the newly opened walkway that passes around the back of the Odeon, parallel to New Street. The under-cover part of the walkway acts as a wind-tunnel, and I had to push against a viscious headwind on my way through. In the plasterboardy gloom is the new temporary bike parking: bolt on Sheffield stands. I parked my bike here briefly in order to visit the shops, and did not find a note declaring it too ugly for the new station's aesthetic on my return, even though it has enormous alloy forks, butterfly bars and a propstand fitted. The area is currently well overlooked by bored Network Rail contractors, and plenty of people pass through it, so I don't think anyone's likely to unbolt the stands during peak hours. A quick attack of the bolts with a MIG welder wouldn't have gone amiss, though.
The exposed bit of the walkway has glass panelling on the station side, so people of normal height can now peer down and watch trains passing through the 'A' end of the station. There's some raised soil on the right, which will presumably have things growing in it eventually. The walkway emerges right up near the Moor Street underpass thingy, where the bus stops are. From here the existing signs point the way to Moor Street station and assorted retail opportunities. After visiting the shops, I approached the walkway from the direction of the old main entrance, and noticed that the large sign pointing to "Birmingham New Street Station" down the walkway is hidden behind a concrete wall until the last minute. Combined with the "Bimringham New Street" sign on the exterior of the old building, I expect confusion, at least amongst people arriving by bus. It's another couple of hundred metres to Moor Street station from here; a significant distance if you're visually or mobility impaired.
In summary: Meh.