I used a set of Nimbus Armadillo tires for a while, but my biggest gripe with them was that the tread had begun to crack and separate from the casing after about 2,000 miles. After the tread started gradually peeling off, I got tons of flats. I should note that the tread itself had not worn much; it was simply coming off (gradually) from the casing.

I've read that many other people have the tread separation experience with them as well. I otherwise liked them, but am scared to go back for fear of this.