Firewire isn't "dying", it's only dropping in popularity. "Dying" makes it sound as though it'll just suddenly stop working one day.
 
Like the belief that XP would stop working when Microsoft stopped supporting it. Or that all the elevators were going to stop working at midnight on 1/1/2000. This isn't like the transition to digital television, where every analog-only receiver did indeed suddenly stop working. Your Firewire interface will continue to work until it doesn't, and in the meantime it will outperform USB by a small margin.
 
At any rate, many manufacturers nowadays are offering interfaces with both Firewire and USB, so you can protect yourself from any sudden obsolescence, real or imagined.
 
As for the "best" interface, well, even if you could get a consensus you probably couldn't afford it. Not unless you've got 4 to 8 grand to blow. Fortunately, there are many models that are plenty good enough for $500-1500. You can't go wrong with RME or Lynx, as stated above.
 
I've recently become an unexpected fan of Focusrite after having to "settle" for a cheaper unit after my MOTU suddenly crapped out. As it turned out, the Focusrite (Saffire Pro 40) has been a fine interface, and in some ways an improvement over the MOTU.
 
Audio interfaces are pretty durn good these days across the board. So good that you might as well choose them based primarily on features (number of ins and outs, S/PDIF, MIDI, etc.), followed by manufacturer reputation and by what you can afford. 

Probably some good prices on some Echo Audiofires on Ebay.... coming from a fellow 3G past user

Hello,
 
I agree with the statement that Firewire is not as popular.  It is still however,  a viable choice.  As with most technology, its honeymoon is short but its usefulness is unique to individual preference and how long it is used. 
 
On a different note, I use the Zed R16 mixer. It has the firewire interface. It is an impressive piece of equipment with more than respectable conversion, excellent preamps, highly useful eq, analog summing capability and great build quality.  I would personally compare it to some of the best names out there (Not calling out anyone in particular) in overall sound performance ... dollar for dollar value without reservation. I think it is one of the best buys out there. A different approach to an interface , been around a bit (2008) but highly effective, versatile and useful... My two pence.....

I swear by my Focusrite LS56, and before that Presonus FS26x26.

Both rock solid.

Cheers,
Jerry

Focusrite. FireWire devices run on thunderbolt. Not dying then and faster than USB 2 devices (still haven't heard of a USB 3 device yet or thunderbolt, has anybody else?).

CakeAlexS
Focusrite. FireWire devices run on thunderbolt. Not dying then and faster than USB 2 devices (still haven't heard of a USB 3 device yet or thunderbolt, has anybody else?).

Motu 828 is Thunderbolt.
http://www.motu.com/products/motuaudio/828x
 
I use both the Fireface 800 and Edirol FA-66 with thunderbolt to firewire adapter and have not had any problems.
 
One thing about thunderbolt connection that bothers me is the cables never feel secure, like they would easily fall out. Though that has not happened to me.

Love my M-Audio NRV10. Very comfortable, stable and high-quality sounding thing. I don't think that USB is suitable for pro audio.

I had firewire devices, with a T.I. firewire chipset in my PC(s).  I started out with an Alesis IO26 but it was a dog and high latency.  I went to a Focusrite Saffire Pro 40 and it worked well, although 11ms was the best I could do with latency for reliable operation.  The Focusrite died out of warranty and the estimate to repair it was within $50 of what I paid for it new so I dumped it.  I replaced it with a Roland Octa-Capture, USB connected, unit.  The preamps are not quite up to the Saffire Pro 40's but very acceptable.  It has features the Saffire Pro 40 does not have and it has lower latency - about half what I could use with the Saffire Pro 40 (I'm using 6 ms but I've went as low as 4 ms without problems). 
 
My backup unit is an M-Audio Fastrack Ultra 8R, with is also USB, and it too has about the same latency as the Roland.  I had to use the Fastrack Ultra 8R several times when I had the Saffire Pro 40, but never since I got the Roland.

imo the new uad apollo (firewire and thunderbolt)interfaces are in the same row with rme and lynz .
My focusrite saffire pro 40 (good sound, good preamps) is running really good  here,
but rme and lynz aso deliver interfaces with shorter latency.
There one has to pay for.
 
Have fun
 

Sadly the "best bang for your buck" firewire interface has been abandoned by Tascam.
The FW-1884 is/was a brilliant piece of gear.
Very good I/O, and a capable control surface as well.
I love both of mine!
 
T