So, today, while my partner happily shopped in Guildford, I dropped into Andertons (excellent store btw with great knowledgeable staff) and picked up the 6i6 to replace my aging Roland UA25.
So far I am extremely impressed. It's not bus powered so the ground loops that plagued the UA25 have finally gone away. It's absolutely silent, as you would expect. Very solid construction, similar to the UA25, aluminium case and all the knobs and sockets look like they can take it.
Since my main usage is to play softsynths, I was very pleased to see that running on my Acer laptop (core i7/8G RAM) it will run three instances of Kontakt playing two pianos and RealGuitar at a reported latency of 3.3ms in Reaper. Probably can load up a few more instances, CPU is ticking away around 10% with that load. This is also plugging it in via a hub (but it is a very very good hub - Pluggable 10 port - it's absolutely excellent. I can run everything off it without any glitches and just connect to one USB port on the laptop).
Also currently there is a promotion so that you get a free download of Focusrite's Midnight suite which comprises a compressor and EQ. Not something that matters a lot but nice to have, I guess...
 
 

Congratulations!!
 
I' am very very happy with my Scarlett 18i20, great interfaces in my opinion.
Great drivers, very good preamps, and latency is great in my system too, I always record audio monitoring with DAW fx.

I hear nothing but good stuff about the 6i6.
 
Good price for the amount of I/O and a good way of getting audio loopback too.

Hey,
 
I've got the 18i8.  It doesn't look like 64 bit drivers are available for it yet.  Do you know if that's correct?  I'm very happy to hear about  your latency report.  That's awesome.
 
Donny

Looking at FocusRite's download site, mixcontrol 1.5 is available for both the 6i6 and 18i8 and I would be astonished if this didn't work on 64 bit windows for the 18i8. Certainly I have both 32 and 64 bit versions of Reaper running fine with the 6i6.

I did get the driver to work with no trouble, but the RME on the PCIe bus was doing alot better.  I got a huge CPU spike when running projects where the RME would stay around 5-10%.  I'm going to stick with it on the desktop.