I also enjoyed the idea of Naruto and Sakura getting together as early as the beginning of the series. At that point I did not like Sakura much as a character, but Naruto stated early on that he really liked her and I wanted him to get what he wanted for once: her. As I watched Part 1 (back in '05/'06), I thoroughly enjoyed seeing Naruto and Sakura's relationship develop from a one-sided crush into a mutual friendship. I especially shipped NaruSaku during the promise of a lifetime scene. The way that he looked at her when she was crying and promised to bring Sasuke back.... Absolutely beautiful. Naruto knew that Sakura loved Sasuke so much at that point that he was willing to put aside his own feelings for her in order to make her happy. That is true love right there.
In Shippuden, I found that Naruto and Sakura's relationship bloomed into a deeper friendship that is slowly turning into something more. She was physically attracted to him as soon as he got back from training, and they worked so well together getting the bells from Kakashi after being apart for so long. The Heaven and Earth bridge scenes as well as their individual confrontations with Sai about their feelings further pushed me into the NaruSaku abyss. It became clear that Sakura cared so deeply for Naruto; she was willing to put her life on the line for him and cared so much about his well-being and happiness (just like he did for her in Part 1).
I think there was truth behind Sakura's words during the confession scene. She didn't realize it at the time, but she was starting to fall in love with Naruto. That's why she was blushing when she told him that she loved him; you can't really force yourself to blush, it's an innate, automatic reaction. Naruto reacted the way he did because he knew that she was still in love with Sasuke and he didn't realize that she really was falling for him (because even Sakura herself didn't fully realize it at this point). It was a sad scene, but it was obvious to me that Sakura had developed feelings for him. Also, Naruto saving Sakura from Sasuke was just a beautiful scene that now reminds me a lot of Minato rescuing Kushina.
I sort of fell off the NaruSaku bandwagon after this. There wasn't really a whole lot of interaction between Naruto and Sakura that made me feel like their relationship would ever blossom from friendship into mutual love. 615 in particular made me lose hope in this great ship; I thought that Naruto had begun to notice Hinata in a more romantic light and had forgotten all about his love for Sakura.
Thankfully, I couldn't have been more wrong.
Sakura's wonderful speech in 630 made me realize that she does deeply care for him and knows him better than anyone else. It was like they were husband and wife: She is so familiar with him and in-tune with his feelings that she was the one to encourage everyone not to doubt Naruto and their alliance. She knew what he was thinking and stepped up to defend him in such a caring way (although the way she said it was definitely not caring toward the alliance haha). And Naruto calling her his girlfriend in the following chapter only re-affirmed his love for her. He told his father, the one he looks up to more than anyone, that Sakura was his "kanojo; his lover; his girlfriend. And she didn't deny it! I can't wait to read the remaining chapters and see how the beautiful friendship between Naruto and Sakura finally blossoms into open love....preferably with a forehead scene.
TL;DR: I do not ship unless I see mutual attraction and development BETWEEN the two characters. NaruSaku has mutual attraction as well as development BETWEEN the two characters, unlike the other main ships.