I have two Western cells and I love the noise free and the stability(if properly maintained). I know someone in the metrology field that prefers cells over solid states. However, the very large tempco may problematic.
There are still a few labs that use Weston cells as their primary reference. And others that have kept the old set as a backup even though not regularly maintained.
From the hobbyist point of view the problem is that buying a good cell is almost impossible nowadays. Unless you get a powered cell enclosure directly from a closed cal lab and hand carry it to your home lab.
Buying from Ebay or from equipment dealer is not an option. High temperature will ruin the cell, low temperature can ruin it, any temperature change affects the behaviour. Turning the cell upside down even for a few seconds can ruin it. Some cells fully recover, some don't.
In one year time scale the drift rate of some good cells can be assumed constant, but in the long run the change is not linear. And monthly comparison is needed to make sure that nothing is going wrong. Sometimes there is a reason for the instability, but often it just happens.
Interesting to play with, but I think we should be very happy that the LTZ1000 exists.