I was genuinely very excited about this book when I read of its development. I thought a supplement dedicated to special, iconic weapons was a great idea during a time when Wizards' D&D accessories have struggled to get an original hook.
I skipped through it first ideas, and my initial impression was that it seemed a bit sword-heavy. Still, best to give it a chance, so I started reading closely... I very much liked the idea of an item growing in power with the character as he/she grows through the levels, and also the idea of performing small side quests to further unlock the item's potential, which usually involve slaying a certain monster or performing a certain feat etc. Somewhat less appealing was the idea that the character must consequently give up or take a universal penalty in exchange for such a powerful item (a -1 to saves or to hit, for example).
But what really killed this book for me however is the meat of it, the items themselves... I found nothing in this book even remotely close to justifying the players expense in terms of power. Much of the flavour/backstory of the items was interesting, but then you get to the statistics and what the player must do to unlock suck meagre abilities... and there my interest started to wane.
In all honesty, the items that can be crafted from the rules presented in the DMG will get you much more than what is presented in this book. Yes, the examples are ok, some better than others, but as I said, if you're looking for "items" of legacy, you won't find much here... no special staffs for example. Either that's simply a matter of poor development or a deliberate omission in order to furnish a future supplement. Wait, what's this? A Magical Item Compendium for 2007? Tut tut, Wizards of the Coast.
To sum it up, Weapons of Legacy has some decent ideas but the rest are either underdeveloped or just unimpressive. Just borrow this one from a friend and put your money into the aforementioned Magical Item Compendium, which, if the Spell Compendium is a good marker, should give you more of what this book should have had.
Happy gaming.