For one, it's great to see what new engineering technology can do for a company. Even as a rabid mountain bike enthusiast, I knew next to nothing about Empire Cycles (and I bet it's the same for most US based riders). Now they're on ABC, Gizmag, CNET.. the list goes on.
Take a look at the seat post above: it's impossible to machine (hollow sections) and probably impossible to cast as well. Being able to design previously impossible to manufacture parts has huge benefits, similar to the benefits that FEA tested carbon fiber components have over traditional cast parts: low weight and increased flexibility to optimize with FEA analysis.
Reinshaw Engineering spent some time optimizing the part and was able to achieve a 44% weight savings over the original aluminum. That's a big deal in an industry where customers spend hundreds of dollars to save a few ounces.
It isn't too unrealistic to imagine a future where a customer can order a custom printed frame tailored to their weight and size (at a premium) similar to the way ski boots shells are custom molded.
It just remains to be seen whether the technology can be made affordable enough for even the ultra-premium customer, but if manufacturing trends continue, that should happen. Will it ever make business sense to mass produce 3D printed frames? Only time will tell.