Thanks for asking!
Flying Faders II isn't out yet (we had to go back and re-complile a half-million lines of code), but we're working on it daily. It consists of a new software version of Flying Faders that runs on Windows XP; this has many features that were developed for Neve but never incorporated. The automation data and timecode connect to the new computer through a little box via USB - nothing changes on the console or servo automation card-cage.
The new system will be an easy upgrade from the old, and relatively cheap. There will be a software utility to convert old mixes to new, but there's no going back.
Current FF, v.3.1, installs with Windows 3.1. We build new 486-based PCs for new FF systems (yes, you can still get parts), and we have been able to ressurect ancient computers with good success. The HP Vipre card (a co-processor card) can't run on a fast computer bus, and these are long discontinued and difficult-to-impossible to fix.
FF faders have always been proprietary P&G dual-track faders, one track for audio (stereo or mono) and one track for automation data.
GML systems were great, but it doesn't seem to be easy to get support these days. Uptown works, but (you'd have to ask them) I believe API is moving on to a new system that they developed for their Vision console. Neve will, of course, add Encore to your existing console, but it will be expensive.
We actually make a FF equipped sidecar, the ACX, with 16-32 inputs, 8 aux sends, eq per channel, etc. (no summing bus or monitor section). This is used to extend an existing FF equipped console or to automate a mix through a non-automated console or DAW (FF syncs with timecode, of course).
I think Digi has it right when they see the need for a large-format control surface, but there are still many engineers who will prefer to work on a moving fader controlled analog console.