If it helps, there is a "My Channels" app that allow you to organize your favorite channels in a semi-grid fashion divided by categories. Before the new GUI, I used to run my favorite channels from this app. I had over 200 channels then (Now 400+) and I HATED the side-by-side icon navigation and this helped me back in those days. Given that you are stuck with the old interface, you may decide to use the "My Channels" app and also move to the beginning and end of your side-by-side channel list your most used Roku channels so you can access them quickly without all that annoying scrolling.
Hope this tip helps everyone using the old Roku interface.
2xRoku2 XS,Roku1+SE,Logitech Revue GoogleTV,Raspberry Pi+XBMC,Mac Mini+EyeTV DVR+RabbitTV+PLEX+Kodi,TiVo Premiere,Sony BluRay+streaming apps,Equiso Android TV,FireTV,Nexus player,Simple.TV Local TV:QAM from ISP coax line. PLEX+unsupported apps