The HR20 guide is far from slow. It is lightning fast. You hit page down and *bam* it's done. You can make it even faster by turning off guide animations in the display options. Now it might not be as fast as the 722 (no idea, I don't have one) but it certainly isn't slow.
As for changing channels, if you are using HDMI and have Native set to on then it can very well take a few seconds if your TV has to resync (which many do when using HDMI). Turn Native off and set the only resolution to 1080i (or 720p if you prefer) and channel changes will be 2 seconds. But it's your choice how you want to go. You can do it fast or you can do it slow, it really all depends on your combination of equipment and what connection you are using.