Things that were discovered that weren't known:
1) glass back
2) appearance
3) high res screen (though suspected)
4) front camera (suspected)
5) camera flash (suspected)
6) increased memory
7) use of A4-derived processor (suspected)
8) noise-cancelling mic
9) microsim
Also, in addition to providing competitors with a 2 month head start on what the phone will contain, competitors also know what the phone WON'T contain.
Additionally, now people are more likely to postpone buying an iphone until its release. Although we all knew something new was coming, the general public didn't. And news of the new features has made it to CNN, the NY Times, etc - the general public is now aware of all this.
don't you have to wait till its released till you can buy it anyways?