Well, after having nearly 100% the game, with only a few heart pieces to go, I have attempted at using the Razor Sword before. I did think that it was an interesting blade, but the downside is that you can only use it for 48 hours or 200 swings. I did get confused at one point, thought the Razor Sword was the Guilded Sword, and tried to Song of Time it. Yeah, that wasn't a wise choice. I figure the Razor Blade is only useful in things like boss battles when you don't have access (and/or knowledge) to the Guilded Sword. I mean, I honestly thought the Guilded Sword was a way better deal than the Razor Blade.
Swords like these make the Kokiri Sword (Which I swear, if Adult Link used it, it would be a dagger to him) look pathetic. I mean, its sad when a stick can deal more damage. Yet, when you think about it, the Razor Sword is worth the price, yet it isn't also worth all of the time that it takes to make it. I mean, if you were to complete a dungeon with it, then it would be bad if you made it up to the boss and have it turn back to normal (In fact, based on all of the puzzles and enemies, it would convert back way before the half point of all of the puzzles).
However, when you really think about it, it is the Kokiri Sword that has more nostalgia than the Razor Blade, seeing as to how that sword went through two games, even though it had a random change in design in three months. So, when you really think about it, the Razor Sword isn't all that bad price wise, but taking a day off of exploring a dungeon can be a bit of a downer. Unless you Inverted-Song-of-Time it.