A lot of users never see the tiny triangle below the web map or Web App Builder map that opens the attribute table. It's just like the one in the Flex viewer, which is brighter (yellow). With Flex, you could set the table to be open on launch, but it took up so much of the screen that I hated to do that. Perhaps AGOL maps and templates could have a bigger arrow on a full-width title bar labelled something like "Tables" or, better yet, customizable. Also, if a feature is selected and the user closes the attribute table, the selection remains and the only way to clear it is to reopen the table. A lot of users won't figure this out on their own. This might be resolved with a Clear Selection button on the table title bar, or a general Clear Selection button that works on any selections in the map or table.