I travelled on one today, and was not impressed.

The good points - bright lighting, smoother ride, more standing space

But the downside of the last point is less seating space. The seating
follows the current fashion of being all sideways, which personally I
detest. Crabs evolved to travel sideways, humans go forwards.
Another drawback is that is much harder to see out of the window. Now
I know that isn't an issue on the Victoria Line, which is all
underground, but on other lines which do have surface sections it adds
to the frustrations of travel. The seats themselves seem to have been
designed for midgets, with inadequate depth for an average sized adult
male and very thin upholstery.

Some tube journeys can be quite long - I have a regular trip between
Totteridge and Whetstone and South Wimbledon which takes one hour ten
minutes, and I wish transport chiefs would pay a little more attention
to the comfort of such passengers rather than basing the designs on
the needs of short distance commuters only.

Peter