5 Excellent

Well, I would like to start off by saying that Anjaana Anjaani is the first movie I have gone to see on its first day. Not the first show though. But I benefitted in another way due to that - I could not read/watch any reviews, so I entered the movie hall with a completely clean slate.
The biggest reason that made me want to see the movie in a hurry are the songs. While we have already had I Hate Luv Storys, another movie which had great songs (incidently Vishal-Shekhar gave music for IHLS too), Anjaana Anjaani feels like a complete album, with a song for every mood.
The second was, surprisingly, Ranbir Kapoor. He has been on somewhat of a roll, beginning with Wake Up Sid, then APKGK, and then Rajneeti. Three brilliant performances and he did not disappoint with his fourth as well.
The final reason - Priyanka and Siddharth Anand. Priyanka, of course is a seasoned actress now, and I dont expect any of her performances to let audiences down and Siddharth, despite Ta Ra Rum Pum, has always shown a promise of making movies which are off the beaten track.
The start of the movie itself (yes, some people might find the start a little slow) shows what lies ahead in the interaction between Ranbir and Priyanka. Starting the movie by showing the lead pair attempting suicide is What I felt was a brilliant story idea. From the days of QSQT, when the hero and heroine would die for their love, to Anjaana Anjaani, where they attempt to commit suicide - wow.
What follows for a few more minutes is extremely predictable. They try various methods to commit suicide together and fail. Then they sort-of agree that its a sign that they are not meant to die right then because of a reason, and so they make a pact that they will commit suicide on December 31, after living together for 20 days by jumping off the very bridge where they met for the first time. What then follows is fun, because they decide to fulfill whatever wishes they can.
The fun is interrupted by something dramatic (or melodramatic, if you please), which makes Priyanka and Ranbir tell each other the reason why they want to commit suicide - Priyanka was cheated upon by her childhood sweetheart Zayed, and Ranbir is a now bankrupt and unemployed due to the stock market crash. Following that, they decide to go to Las Vegas. More fun/adventure happens on the way. Incidents in Vegas make both of them realise they might be falling in love but they also are compelled to not tell this to one another. Then while returning to New York, Ranbir decides to do the right thing while Priyanka is asleep. The choice he makes is painful for both of them, but neither says anything. The Las Vegas trip has been compared to the DDLJ Euro trip in many reviews and feedbacks, which I felt was erronous, because here they actually travel because its Priyanka's wish, rather than taking an expensive holiday roaming all across the continental USA. In fact, when they do travel to Vegas, they do not have any significant amount of money, which I thought was rather brave of the director.
What actually happens at midnight on 31st December is very predictable, true, but it is in such a way that it is not brain-defying logic and it can/will be loved by the audiences. Or maybe, a few potions of the film are predictable. However, that should not, and does not, make a difference in its quality. It is a sincere and heartfelt effort by the whole crew of Anjaana Anjaani, and it touches you as so.
The cinematography, lyrics, music, story, screenplay, dialogues and direction deserve tremendous credit, as do Ranbir and Priyanka (and maybe Blush, the car too). In fact it is to the credit of the two actors that the film looks and feels and is so good. And the key to that performance is that they transform themselves into the character they are playing. SO, from frame one, you have Aakash on screen, not Ranbir Kapoor, driving a Mercedes or some super wheels like that. And it is Kiara, and not Priyanka, that infuses energy and charm in the first half. How I wish more actors would be so committed to their characterisation. Praise also goes out to Zayed Khan for the underplayed performance. It was the first time I discovered that Zayed could also 'not shout' in every second scene.
But there is one thing that audiences might complain of; and that is Ranbir playing the 'guy who hides his feelings from the girl he loves' a little to often recently. It might also appear like a combination of Wake Up Sid and APKGK (come to think of it, its similar even to Jab We Met), and there may be some justification in that too, but neither of those movies was such a heartfelt (read pure/out and out) love story.
So, those who have always loved to watch a love story on screen are certainly going to get more than there tickets worth from Anjaana Anjaani.
And those who complain that about the predictability factor, just remember that DDLJ was not the first movie with a love story in it.....