I've had my Zephyr (Black/Black/Steel) for just over a year (time flies!) and have used it every work and travel day. I absolutely love it. I got the absolute shoulder strap for carrying it, which is absolutely fantastic.
I chose the Zephyr over the Empire Builder and the ID.
I chose the Zephyr over the EB because I didn't think I'd need the extra space that the EB has and I wanted the smaller footprint. I haven't once wished for more space and am happy with that decision.
I actually also ordered the ID because I wanted to have both in my hands for comparing. I returned the ID ultimately because I felt like the Zephyr looked a bit more professional. If I had been choosing a bag solely for traveling, I would have chosen the ID because it was lighter (due to the less structured) and because of the water bottle pocket. I miss having the water bottle pocket, but that was one piece of the ID that looked less professional than the Zephyr.
After one year of use it looks as good as new. It holds an amazing amount of stuff and never looks overstuffed. I knew it was going to be structured, but I didn't know exactly how much structure there would be. The structure definitely adds weight and makes usable space a bit smaller, but IMO it was worth it because I can put manila folders with papers in them in the bag and not worry about them getting all wadded up.
The Zephyr joins my Aeronaut and Small Cafe Bag. I love both of them too!