I've owned swift-key since its early days when it was the Amazon free app of the day, and later bought from play store when it was on sale for $0.10 so I could update quicker (Amazon is usually months behind on updates). I've also used Go keyboard, stock GS3, and nearly every other free keyboard available.
For word prediction and for touch typing, I think swiftkey is by far the best I have ever used. When I turn the phone landscape and actually type, this is awesome. However, I think the "flow" is far inferior to swype. As someone else pointed out, after each word you "flow", swiftkey offers the next word as a prediction, while swype looks at other options for the word you just swyped, allowing for much easier corrections. Also, swiftkey likes to put two words where I am only swyping one word.
So, if you plan to type more frequently, I think this keyboard is great. But if you are buying it for the flow, save the $2 and get the latest swype beta.