I fear I will forever be looking for another 410, 420, 510, or 520. The loss of the chapter mark button on the 633 largely impairs my use of the unit, and it sounds like the 640 doesn't have it either. But more troublesome to me is that the 633 does not play title to title. I leave my DVD to playback alot, and I have speakers throughout the rooms so I do not have to monitor the playback. On these older models, once Title 1 finishes playing, Title 2 starts. I am new to the 633, but after it finishes a title, it pauses for a bit, then defaults to the TV channel it was last on. Does the 640 do this? Do any 633 owners know how to change this? The manual says nothing (it adds the instruction that playback will stop after a title plays), and while there is a feature called 'seamless playback', this is not what it references.