Features:
I'll give you a quick background of Tapco, taken from my Link.USB review:
Greg Mackie started the Tapco company in 1969 but a number of years later sold it to Electro Voice. Electro Voice had been the owners of Tapco throughout the late 1970's and into the 1980's. During that time, Greg Mackie had worked on a few other projects before starting the Mackie company we all know today in 1989. Eventually however, Electro Voice folded Tapco and gave up all rights to the name. However, back in 2003, not that long ago, Tapco was reborn again, this time under the Mackie umbrella. Their aim has always been, and still is, to provide affordable audio products to their consumers. With that brief history, you'll understand why the Link.Firewire has very heavily Mackie influenced styles (such as the pots on the front seen in the image below) and Mackie designed preamps.

Unlike the Link.USB which was only 2 inputs and 2 outputs, the Link.Firewire is now a 4x6 interface. What this means is that you have 4 inputs; 2 mic preamps/line inputs and a digital SPDIF connection which is 2 streams of audio, and for outputs you have 6; headphone output (L/R), main analog outs (L/R) and digital SPDIF (L/R). Having the digital SPDIF connection is excellent for adding extra inputs such as a digital mic preamp, digital audio player, effects processors, etc. Anything that supports digital SPDIF should work with this. Same with the digital outputs, you can now hook into equipment such as digital monitors, digital receiver and much more!

 
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On the front of the Link.Firewire you'll first see the two input control areas, surrounded by yellow borders to match the gain pot colours. These are both switchable between Line Level and Instrument level so you can easily directly connect things such as guitars to the interface for recording. Each Mackie designed preamp has 48V phantom power which is switched on with a master switch between the two gain pots. I was happy to see the addition of a signal and overload LED for each input that switches between green (signal) to red (signal clipping) when needed. To the right of that is the monitor volume pot and next to that is the headphone volume pot with the headphone jack. I liked the little chrome coloured "roll bars" at either side of the front. These are great if you're moving or travelling with the Link.Firewire and will help prevent the knobs from getting damaged from any sort of front-on collision.

A little more on the technical side again; the Link.Firewire is capable of recording at 24bit/96Khz. An impressive spec, especially considering most people probably won't be going much higher than 24-bit/44.1Khz, but it's always nice to have the option to go higher if you please!

Another handy ability to help save a little desk space is that the Link.Firewire is fully bus powered if you have a 6-pin firewire connector on your computer. If you're using a system that doesn't support bus powered devices, Tapco was nice enough to also include an adapter to power it from the wall if needed.

The Kensington lock port was a nice addition and can provide some extra security if you chose to keep it safely locked to your desk.

For those who don't want to operate the Link.Firewire horizontally, the side chrome bar you see in the pictures actually swivels out to be a foot so you can stand it vertically (seen below).

 
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