Hi there!
I actually just have a few magpies from Holderread, and I do love them. I had planned to breed them, and probably still will, but other things have taken precedence in my life lately. Anyway, they are gorgeous and ducky, of course, and mine produce eggs every day, better than the Indian Runners even. BUT, that is probably because my runners are hatchery stock while the magpies are Holderread. I HIGHLY recommend Holderread stock to start with. I've seen photos of magpies from other hatcheries, and the markings are always all wrong, and they simply look like small anconas (which are gorgeous birds, but they're not magpies).
The eggs are a classic creamy white in a standard egg shape (versus runner eggs, which tend to run toward bullet-shape). They are not as hardy as the runners, in my experience, but then I'm not sure any bird is as hardy as the runner. The only time I've had problems with them is when I've made a mistake or had bad luck (such as a bad batch of feed)--but then it was always the mags who showed symptoms and suffered the worst versus my runners. But again, they are generally very healthy and hardy, just make sure their feed is right lol.
I'd be glad to answer further questions. I'm thinning my flock and only keeping the magpies, so that should tell you something about how I feel about them.