Quite the trade-off, so instead of shaky unaligned horizons you now get irritating zooms effects [1], plus up to more than 2/3 of the original frame missing? (at least that's what the online demo represents).
At least the constant zooming could be easily lessened by defining a safe area of the frame as the active content while using the remaining sensor area for compensation only.
As a Horizon user, it bugged me that so much of the image was cropped to ensure stability (portrait width in landscape orientation - grrr). The rotate-to-zoom effect isn't perfect, but at least it gives the option to use more pixels when available (and I'll take zoom over wobble). Otherwise you're using an HD camera to take stable SD video.
You do have the option of turning off rotate-to-zoom and stick with the prior low-res stabilized image.
We have implemented a solution to the problem where the crop area zooms in/out smoothly in Flex mode, so that the wobbling problem is reduced. It will be available on the upcoming updates and in the Android version as well (hint! ;)).
In the meantime, you can switch between modes while recording depending on the situation. Finally, locked mode switches automatically to horizontal or vertical orientation in version 2.0.
At least the constant zooming could be easily lessened by defining a safe area of the frame as the active content while using the remaining sensor area for compensation only.
[1] http://www.horizon.camera/demo