I went along to Waterloo this morning and took a few pictures:
https://www.flickr.com/photos/recliner/albums/72157684802951344

A few observations:

- It was moderately busy, but no problems. Lots of blue-vested helpers
around, but they didn't seem to be needed.

- Many trains in the former international platforms are delayed by a
few minutes. Even if they leave on time, they get delayed on the way
out, presumably because the current track layout isn't optimised for
domestic trains. Maybe they'll change it after the Southeastern trains
have finished using it next month?

- The international station is still very much a building site. Only
part of the new concourse is open, and you get to it by a temporary,
fenced-in bridge. Work continues on the new retail area beneath.

- All of the platforms 20-24 are accessed through the same gateline,
which is in operation. It was reminiscent of the new London Bridge low
level platforms gateline.

- I saw no sign of a direct route from the new concourse to the Tube
lines below, but there's so much work yet to do, that it may appear
later.

- I got the impression that platform 20-24 are slightly lower than the
UK norm (such as it is). The step up to the train seemed slightly
higher than usual, though the curved platforms make it worse. I
couldn't see any sign that platforms had been raised.

- A jobsworth immediately stopped me taking pictures of the
construction work taking place beyond the closed platforms' gateline.
He seemed to have been placed there specifically for that purpose;
nobody stopped me taking pics in the station public areas. But what
struck me was the construction material trains are parked right up to
the buffers, even though I thought the platform rebuilding was taking
place towards the country ends.

- As an aside, I noticed that all four Battersea Power station
chimneys have been rebuilt, and look pristine (unlike the rest of the
battered old building).