Hm, I may as well throw my two cents in here (though I think all opinions have been covered so far).
Honestly, I'm GLAD Sakura did this. It creates drama, and drama creates character development. Now, Kishi just has to follow through with this. Honestly, I think Sakura does have feelings for Naruto. Maybe not so much romantic on a 'I love you' scale, but it's a slowly progressing thing. She wasn't lying about the fact that Naruto has been a constant support for her, and a dear friend, because he has.
I think the main point here is she wants Naruto to be safe, so she's trying to pull every card she can out of the book to keep him safe, including giving him a (very) long awaited confession. Unfortunately we have a case of bad timing, and the fact that Sakura's a bad liar, which in this scenario is a bad thing for her. Naruto obviously knows she isn't being totally sincere. Sakura was still a bit torn between Sasuke, even after three years of him being missing.
In the end, I think it all boils down to that Sakura told half a lie; she cares for Naruto more than she does for Sasuke, but she doesn't necessarily like Naruto in a romantic way. I think she'd willingly take kunai to the chest for him, but that's just a natural thing you would do for someone who is such an important person in your life. Sakura's in a transition right now; she's been changing since the beginning.
At first, she was head-over-heels for the Uchiha.
After awhile, she began to see that Sasuke has a history that's been bothering for awhile, she never knew what it was though. She began to genuinely care for him. She also began to see who Naruto truly was; a loyal friend and someone who will go the extra mile for those he cares for.
Sasuke left, and Sakura turned to one person over all the possible people in the village. Not the Hokage, not Kakashi or one of the other Jounin-sensei, but Naruto. She saw Naruto as a person who can turn people's hearts, shake people's images of him, and surpass his limits every time. To her, Naruto was her pillar when Sasuke left.
With Sasuke gone, Sakura began to truly realize that the Uchiha was heading down a dark road, though she probably didn't know the full details, blaming it on the Curse Mark and whatnot. Naruto came back after having been stabbed in the lung via Chidori from his closest friend, and she knew that Naruto was suffering as well from this betrayal. Sakura said that next time they'd go after Sasuke together.
Fast forward two and a half to three years, Naruto and Sakura both have improved. They show their improvements to Kakashi, go save Gaara (critical point for Sakura, since she killed Sasori with Chiyo's help, making her the first ninja to kill and Akatsuki member). Sakura also learned of Naruto's darkest secret, and she came to see Naruto, yet again, in a new, and probably more profound light. She began to feel a stronger desire to protect our blond protagonist in the Rescue Gaara arc.
After chasing a lead on where Sasuke could be, they encounter their old comrade and teammate, only to see he's become rather cold(er) and openly stated that he spared Naruto's life on a whim back in VotE. He attempts to kill Naruto, only to be stopped by both Yamato and Sai. Sakura sees that Sasuke truly has changed for the worse, and this time she is the one to help support Naruto, since he was both angered and frustrated at missing an opportunity to bring back Sasuke.
I could go on with other examples. Sakura has clearly shown time and time again that she's grown fonder of Naruto. I think we're going to have a real bit of shaky drama soon though. Naruto's clearly not buying the 'confession' Sakura is giving, and he's a bit distraught with her doing so. I think part of it is because he's USED to Sakura caring for Sasuke. His norms are being thrown out of whack. Clearly though, Sakura is lying to a degree. He's assuming she's lying about the confession in general, but I think Sakura's just not giving a whole-hearted confession simply because she doesn't know what to think herself. She's probably trying to convince herself that Naruto is her guy; in due time, I'm hoping this will be true.
...wow, I didn't mean to type this much. Crap. Well, long story short, Sakura cares for Naruto, but not entirely sure on what degree or she DOES care for Naruto that way, just not ready to confess and gave a half-hearted confession, and our blond isn't entirely sure this is possible since it's going against everything he's been working for for the past 3+ years. I think one of them is going to end up making the other come to their senses. Sakura's thrown her hand down, now we'll have to see what Naruto's going to do with catching her lying to herself.
*sigh* Ah, teenage angst and drama. Kishi, please don't fail us with this one. I want a NaruSaku, but hey, I can stand a bit of drama too. Tears, bitter words, and apologies are always nice too!