Seamless charts are nice but I actually see the full chart as a valuable feature. Many charts on apps are not well joined and have different sized text or objects. I'm not saying don't include it, just have the option to see the surrounding info.
Stuff that I like to have from the legend and surrounding area of the sectional/tac are Class B routing information/ Moa/Prohibited times (I really like to use the chart times not the stuff in the database for restricted areas). Grand Canyon for example has a ton of information on the sidebars that is not in the database. I just flew up there last week and the paper chart was out becuase Garmin Pilot wasn't giving me enough.
Every once and a while you see something weird on the chart like "laser test site" with a crazy symbol and it's nice to have the legend.