Hi
Since not many are willing to pitch in

let me give you my feedback.
(Note, this is based on our systems here, depending on your system and taste, YMMV).
Long story short.This type really really shines in TriodeFet systems, and in our phonos.Used DUAL in Quint and Essentia, is probably among my top 3 combos for these amps.
Used single in Ithaka and Kirke(in TF stage), it's presentation is between E280F and E810F. It is a great alternative although i do not use the russian in these two.
On Aperio, i prefer it over the E810F.
On Helene, it is same level as E280F but different presentation. On Kassandra, i do not prefer it over other types and is quite behind.
On phono stages. Now this was the big surprise. We now standardized it for our phonos, for in Input and Riaa stages.
Just my 2c.
Best
Stavros