Finally had a chance to spend about an hour with the new Steinway, and I have to say that I really, really like this piano. The tone is so warm and mellow and the playability is fantastic - possibly the best so far from VSL. I love how the decay time is ever so slightly shorter than on a modern piano, but not so much that it feels like a completely different instrument. The tone is undoubtably vintage and from an earlier era, but it still has enough in common with a modern grand that it feels both comfortable and refreshingly different at the same time.
In regards to the una corda, I don't know if something went wrong, but I'm struggling to hear any difference in tone when the una corda pedal is engaged. Could be an early release bug that needs to be fixed in a future update, but if there is a different set of una corda samples, the difference is so subtle that I'm not able to reliably pick up on it. Maybe others can chime in if they are hearing the same thing?
That aside, I'm really liking this and think it's a winner overall. I hadn't been too enthusiastic about VSL's last few releases (particularly the Fazioli F212) so this is a welcome return to form, and I can see myself getting a lot of use out of it.