Great plugin! One bug: if you're viewing a group's pages, the "Add pad" link currently creates a pad that belongs to the logged in user instead of the group.
Change line 44 in mod/etherpad/pages/pages/owner.php from
$url = "etherpad/add/" . elgg_get_logged_in_user_guid();
$url = "etherpad/add/" . elgg_get_page_owner_guid();
In my Elgg installation (1.8.8, but also 1.8.6), only the pad creators can edit a pad, regardless of the "Write access" settings. I had to disable the access control for pads by hacking line 160 of the ElggPadd class (just changed getReadOnlyAddress into getAddress, but that's not satisfying).
Any ideas why canEdit() fails even if the write access level is set to "Logged in users"?
(I have "Restrict pages to logged-in users" enabled in the advanced admin settings)