I've had the Surly Knards for a few months now, and it's time to spread the gospel.
First, some info about the tire itself. The minimal tread pattern is the same as the Knard in its original size and dimension, the 29+ version that serves as the standard for 29+ tires as a whole and comes stock on its Surly Krampus. (Full disclosure, I also ride a Krampus. I really like this tire.)
Surly issued the Knards as a great cyclocross tire for a new bike, the Surly Straggler. The Straggler certainly describes what the Knard works well for; turning a 'cross bike into a more well-rounded steed in more difficult conditions.
And that's exactly what it does. Pumped up to rock-hard, it's a decent tired for riding pavement, especially with its low profile tread. But take the air out-and take a lot out- and it's perfect for even the loosest gravel roads and even the roughest trails, or at least as perfect as you're going to get on a rigid cyclocross bike.
The tire comes in a 27tpi and 120tpi, with the latter serving as the tubeless option, depending on your rims. While the tire is a 41mm, the width of your rim will influence the actual diameter of the tire mounted. We measure the tire at 37mm on a more narrow road rim, and 42mm on a wider road rim, and 43mm on a 29er rim.
Like your mountain bike, getting the tire pressure right is also a big help. For the Speed of Light, I run around 28psi, and 33-35 on gravel roads. They've are especially good in dry conditions, and are perhaps a bit lacking in the mud or wet black soil, mostly because of the less knobby tread pattern. But even then, tire pressure seems to have a bigger impact than the tread itself.
The Knards are a great pick as an all-around, incredibly useful tire for your cyclocross bike. If your bike will fit these tires, they're certainly worth checking out.