Actually, Horizon Treadmills always receives good reviews by many with knowledge of the industry, as it's a solid built machine without the lofty price you might expect for it. The treadmills are marketed to mid level people, not dirt cheap but also not extremely expensive either.
Since the company has been around for longer than twenty five years, they certainly know what they are doing. The good thing about Horizon Treadmills is that they are put through some rigorous tests prior to being sold, which helps you know they are quality.
One of the great things about them is that they have a fifteen to twenty five year warranty, depending on which you select, which definitely shows they have a lot of confidence in their machine. The ever popular Proform only has a three month warranty, just to give you a point of reference. Fifteen to twenty five years is certainly as long as any company around, so you can be confident in the quality you are getting.