The Horrors is an idiotic Cthulhu nonsense that has no place in SR. Cthulhu is fine in certain circumstances. As far as I'm concerned, this isn't one.
Whether you like it or not, the cycle of magic and the dangers it brings have been part of Shadowrun since the game's inception. If you look back at the early days of Shadowrun, hints about an ancient magical past and dangerous bad magic and creatures started cropping up long before Earthdawn was published (Bottled Demon, Universal Brotherhood, and an early SR short story written by Jordan Weisman). This very dark and dangerous aspect of the Shadowrun universe is an integral part of the game, and always have been.
For you to suggest that a fundamental part of the SR universe doesn't belong tells me that you really don't really understand the game and what it's about.
And for the record, the Horrors are not "Cthulhu nonsense." The Horrors from Earthdawn and the monsters of the Cthulhu mythos are very different on many levels. Once again, this statement demonstrates that you really don't know what you're talking about.
That being said, personally, I don't think any of the Named Horrors from Earthdawn (with the possible exception of Verjigorm) really belong in Shadowrun, but the danger that the Horrors in general represent (even if they are appearing *very* early in the cycle) definitely belong in Shadowrun. Perhaps they shouldn't play a big part in the current meta-plot, but they shouldn't simply be dismissed either.
Take Care,
Lou Prosperi
Who worked with the people who created Shadowrun