It's an experience that is very close to going barefoot. There's no padding at all; just a thin layer of rubber between your foot and the ground.
Things I notice:
1) You're forced to land more on the balls of your feet, rather than your heels. This is one of the alleged benefits of running barefoot or close-to-barefoot. That is, you weren't meant to land on your heel when running, since it jars all of your joints. Almost all running shoes have thickly-cushioned heels that essentially force you to land on the heel whether you want to or not. But when you run near-barefoot, you just can't land on your heel because it is too painful to the heel.
Landing on the balls of your feet is much harder your calves at first, but once the calves adapt (so the theory goes), running is much less jarring, given that the shock is absorbed by the springy arch of your foot, the muscles on the bottom of your foot, and your calves. This seems to be true so far.
2) After just a few weeks, I seem to notice that I'm a lot faster. Not that I'm a very fast runner, but just a month ago, I ran a 3.44 mile route whose halfway mark is at the top of this long and steep hill (the top is about 100 yards further than is visible in this photo):
The time was 25:56, and at that point, it was my best run on that route by 6 seconds or so, but I had been stuck at about 26:00 (or slower) on that route since last November.
Yesterday, after three weeks running in the Vibram shoes (most for sprints and shorter intervals), I ran that 3.44 mile route in 24:53, cutting more than a minute off my previous best time. This feels like a quantum leap forward. Also, I ran the first mile in 6:31 (my pace always slows down after the huge hill), and that mile felt very comfortable, whereas every other time I've run a mile at that pace it's been close to an all-out effort.
Of course, the weather has also been getting cooler, and I notice every year that after a summer getting acclimated to running in 90-95 degree weather, running suddenly starts getting easier and faster in the fall. So maybe that's happening a bit too. Still, even last fall on that same route, the most that I had cut off a previous best time was 35 seconds, not 63 seconds.
3) The first couple of weeks, my feet were very sore and blistered from the lack of padding in the shoe. This week that's not a problem at all. I also notice the darndest thing, something that I would never have imagined. After I run 3 or 4 miles in the Vibram shoes, pounding the pavement on close-to-bare feet, and I then come inside the house and peel the shoes off, my hardwood floor actually feels cushiony to the bottoms of my feet, like one of those rubber mats in a gymnasium. Literally. Of course, the hardwood floor hasn't gotten any softer. It's that my feet have developed some natural padding at least for the duration of the run -- maybe it's just some extra fluid or something, and the effect disappears after a minute or two. I never knew the human body could do that.