Re: #1 Factor in buying TV DVD's?
One thing that influences my purchases is the subject matter of the series in question. For example, "Hawaii Five-O" has been a long-standing classic for more than 40 years (though it only ran 12) because of its rich writing, Hawaiian scenery, opening titles, music, and the general format of the series-- a special investigative unit solving crimes in the 50th state. Now, sure, I wasn't born then, but that hasn't stopped me (for one) from purchasing all of the currently released seasons and seeing and appreciating for myself why "Five-O" was the classic that it was.
CBS DVD has also done right by the series on a technical level, with great transfers, great packaging of the releases, and great menus, among other things.