Hussar
Legend
No, it really doesn't take a huge amount of work at all. In fact, it's incredibly simple.
For my latest lowish fantasy game, all I did was finish the game before the PC's got above about 6th-7th level.
So, basically, to get your lowish fantasy game in D&D, it was so simply that you had to throw out 3/4 of the game?
I can do low fantasy in 4e with one house rule. All PC's must be martial source characters. Done. I can play 30 levels, not chuck out anything. Might have to fiddle a bit with some of the expected bonuses, and of course, pick and choose what opponents to use, but, that one house rule, that doesn't force me to yank out most of the rules in the book, makes a lowish fantasy game in 4e.
Which, I believe was always my point. If you have to massively rewrite your game to serve the game that you want to play, why not pick a game that works?
I also find it incredibly ironic that Raven Crowking, someone who has repeatedly stated that he needs SIX HUNDRED PAGES of house rules for his 3.5 game, would then say that it's easy to change D&D to fit a different model.