Just to correct a slight inaccuracy above, Marathon Plus tyres are lined with up to about 5-6mm of plastic inside the tread of the tyre. They aren't indestructible but they are pretty close. On my mountain bike I had a pair of them and on group rides it was far from rare to stop because someone had a puncture and while they fixed their puncture I'd pull an inch long thorn out of the side of my tyre and throw it in the river. With M+ tyres I ride over whatever debris is in the road and don't worry about it.

On my road bike I've been using them for the last 5000-odd miles and had one puncture, caused by a half-inch hawthorn spike that just went straight through. They're a devil to get on and off but once they're on you won't be needing to take them off very often. Some people say when it's time to take them off it's easier to just buy a new wheel...

I took mine off yesterday to experiment with a lighter weight tyre although the lightweight tyre flatted after 3/4 mile due to a tiny small stone. Taking those off and putting the M+ tyres back on took me about half an hour.

The downsides of using the Marathon Plus tyres are that they are heavy so if you're used to lighter tyres you'll probably find you lose some speed. You'll gain some of it back with each pointy thing that used to have you at the roadside fixing another flat and now just flicks off the tyre behind you.