For the price, you will not find a better substitute. They are comparable with some of the more expensive brand name coated strings and give them a good run for their money.
Sound wise:
When they first go on they don't have the brightness of typical strings, instead sounding more like strings that have been worn in a little. Which is a positive or a negative, depending on your particular preferences. Overall they imparted a tone that is slightly darker than uncoated strings, but not drastically so, id say it's more that they enhance the mids and bottom end more than the treble. But it's nothing that can't be fixed with a bit of eq'ing. They do, however, last a good bit longer than the uncoated strings which is great value for money?
Feel wise:
I couldn't tell any real differences between the coated and non-coated strings, they just felt the same to me, so take from that what you will.
Overall:
I'd you're in to coated strings then you should definitely give these a try and you could find yourself saving a small fortune!