I was looking forward to seeing 500 Days of Summer when it was in the theatre last year because I'm a big Zooey Deschanel fan. Seeing it again now that it is on DVD reminded me why I loved it so much.
#1 the outfits - I loved Summer's vintage clothes and Tom's hipster combos of shirt and tie with a zip up hoodie.
#2 the color - There aren't many movies that make such good use of color. There are some scenes like the greeting card conference room where you realize everyone is wearing shades of grey and beige. Then there are some scenes like Tom's "morning after dance" where blue makes an impact.
#3 the music - of course we get to hear Zooey sing but the rest of the soundtrack is great too... a mix of eighties classics with new indie hits that really help tell the story. Tom mentions how he hears music when he sees Summer - cue "She's like the wind".
#4 creative story telling - the timeline jumps around from day 1 of the 500 days to day 345. Scenes are repeated with different points of view. It doesn't get confusing, it adds richness to the story.
#5 actors - other than Joseph Gordon-Levitt and Zooey Deschanel the other actors are relatively unknown. They all have great performances from Tom's 30 year old in a 13 year old body's sister and his kooky friends.
If you can't tell by now, I absolutely loved this movie. There are some movies that I could watch over and over and this is one of them.