I agree, and VERY easy to teach! I taught it similar to how Jason describes, but with Halo I didn't even need to toss a treat on the mat at first. I just put the mat down and she was naturally curious and went to check it out. I clicked and gave her a treat for putting a paw on it, and released her off. We did that a couple of times, and then I waited until she had at least two feet on it to mark and reward and release. A couple more times, and then all four feet were required for the click/treat.
I had two bowls of treats on a shelf nearby - her normal kibble and cut up Natural Balance roll. Stepping on the mat earned her a piece of kibble as the treat. Once she was going right to the mat and putting all four feet on it, I gave her the "down" command, and rewarded her with the NB roll. I only had to do that a couple of times before she realized that standing or sitting netted her only kibble, but laying down got her a much yummier treat! And voila - we had an automatic down on a mat she'd never seen before, in a single training session of less than 10 minutes. After that I worked on sending her to the mat from further away, and also with the mat in different locations in the house to make sure she understood that she was to go the to mat, no matter where it was, rather than to that particular spot in that particular room.
I had been rewarding her for putting her head down on the floor for a few weeks, in the evening while we watched TV, (I had already taught Keefer with the "calm" command by capturing him in the act of doing it, and she picked it up by watching him), so it wasn't long before the automatic down on the mat included her being "calm" - I think this was the 3rd or 4th day of mat training:
We were not actually going to teach this skill until the following week's class, but when the trainer told everyone to bring a mat to class next week I pulled out Dena's old mat the next day and started working on it. By the next week when everyone else was tossing a treat to get their puppy to get on the mat, I was saying "go to your mat" and pointing to it from several feet away, and she would run to, it spin around to face me and slam herself into a down, LOL!