I have the RME UFX and would highly recommend it. 

This is a tough question because every issue of "Sound on Sound" or "Recording" magazine has another batch of interface reviews and they are almost always positive.
 
MOTU has been good to me, and people I know love Scarlett but I don't recall on comments about latency and VIs.
 
I do almost all VIs and have to change my ASIO setting when I am tracking to get latency under control (and then back again for mixing).  I'm sure you already know that.
 

I've used an RME Fireface 800 since Windows XP and now on OSX and it's been relatively problem free. I say relatively because there was some issue at one point with corrosion on the line inputs. It was a known issue and RME fixed it for free. But as far as software goes it's been good.
 
Even though the preamps at the time where supposed to be pretty good, I've found them to be very flat and dead sounding compared to a Tascam M2600 which is only a very average mixing console. I really don't use the mic pre's on the RME.
 
As far as A/D conversion I really can't tell a difference between the analog signal and the digitized conversion. So that's good.
 
Latency for soft synths has never been a problem.
 
I would not have any issues with purchasing another RME.

I have had a bit to do with both Focusrite and RME and the newest Focusrite models are real nice as RME as has always been very good too.  The latest Scarlett models are getting excellent reviews and amazing latency performance as well. Clarett is still a lavel better though no doubt about it.
 
And to WDI be careful with MicPres that sound bright.  It is often a sign of an inferior Mic Pre.  I have found over the years the the real nice Mic Pres have a very smooth and warm sound actually. I would think the RME Mic Pres are much better than the Tascam MicPres. Try recording through them and see.  (an example is the Roland VS700R audio interface. It has this super warm sound. At first I thought it was lifeless compared to say a Yamaha digital mixer Mic Pre but after a while I got real used to it and realised it was actually normal and the Yamaha was over bright)
 
Thunderbolt is amazing by the way. I have just got an iMac and running Studio One on that as well as my Windows setup. Thunderbolt is fast and I mean fast.  So far it is the best response playing wise to virtual instruments that I have ever encountered. 1.2 mS at 44.1K folks!
 
I have got an RME interface and love it and lately I have been working with a borrowed Fireface 800 and it too is real nice as well. RME are great at supporting older models too with the latest OS systems. Something that should be taken into account.

I've used a a few interfaces over the years: M-Audio 2496, EMU 1212M, Roland V-Studio 700, ESI Juli@, and now an RME Babyface. And the RME is far and away the best I've ever worked with in regards to stability, sound, efficiency and ease of use. I am a total convert to RME, and I can't see me buying anything else going forward. 

+10 for RME

• RME
• MOTU is a close second

 
Both RME and MOTU offer low round-trip latency.
 
RME audio interfaces are more expensive, but it's the type of interface that'll last a decade... and you won't give it a second thought.

Interested in this thread for a friend of mine who is wanting the same thing while keeping the costs under 700. Does the Babyface offer this same kind of latency performance as the others mentioned here?

Lynx

musicroom
 Does the Babyface offer this same kind of latency performance as the others mentioned here?

yes