Reading the topic I fail to understand entirely why a level editor at launch will be a big deal either way...
On the one hand, people sometimes will be more inclined to buy a game if it has an editor, depending on how creative they are and the general capabilities of the editing. On the other hand, if you release it later on, people will still be equally inclined to play or not play the actual game, it just depends on what they intend to do originally. I don't see anyone who actually wanted to play the game....not playing the game...editor or not. Making people wait for the editor is silly to me personally because other than limiting people to the main game until you release it, the end result is going to end up the same, unless of course you actually need more development time on it, in which I can see a valid reason for waiting.
Point is, if people are going to skip to the editor right away, they will do so once you release it if they see fit to do that originally anyway. It might even make people wait to buy it if you say you 'intend' to release an editor at a 'later date'. People are funny like that, but my point is that if they wanted to ruin the game by messing about in the editor, they will regardless of when you release it. So to that extent, why wait?