Just make sure you have an HDMI connection on the TV for the Roku to plug into, some very TV's don't. There are several Roku device price points, we bought one of the cheaper ones, one near the top and one at the top of the line. Can't tell the difference between the resulting picture, all are great.
When cutting the cord, we found a huge increase in quality just in using roku. I agree, not much difference across the roku platforms. It was shocking how much better the picture quality was vs cable and made me feel even more like we’d been getting ripped off for the last several years!!