As a seasoned (read old) editor, I never drag clips from the source monitor or bin to the Timeline but I am am testing 8.6 before a new bunch of fresh-faced students show up at my university in a few weeks. They, of course will drag everything everywhere.
Before the new timeline display arrived in 8.5, clips that were dragged in could reliably be snapped to head and tail frames using Cmnd or Cmnd+Option (Mac). In 8.5. and 8.6 (just checked both), holding the Cmnd key will not snap a clip to the head of an existing clip. What seems to be happening is that the landing position is offset by the duration of the clip being dragged - so if I drag in a 5 second clip, it ends up exactly 5 seconds from where I try to snap. This does not happen if Wireframe dragging is turned on in the Timeline Settings (this reverts to the old behaviour) or if an existing clip is dragged. The only time this works correctly if dragging from a bin or monitor is if you snap to the position indicator.
Tested on 8.5 and 8.6 on two different systems. New settings were used. This is a royal pain for someone teaching (in addition to the lack of full logic and functionality in the 'Smartish' tools).