It's refreshing to have a movie about teens in love that doesn't rely upon sex to gain the viewer's interest. I love this movie, have probably seen it a a few dozen times, especially in the original, unedited version (that wasn't shortened to fit into a two-hour TV time-slot). It's a classic story, but told from a timeless perspective---the movie first ran in 1987, yet there's extremely little in it that would make it seem "dated."
Mary Stuart Masterson is, as always, superb in her performance. While this is one of her early films, it shows her enormous ability and potential. She plays a playful, feisty, street-smart character that also has a sensitive, shy, and deeply loving side. Mary Stuart's kissing scene is one of the most wonderfully romantic and intense kissing scenes on film that I've seen, yet it has an innocent quality that makes it all the more special.
Eric Stoltz and Lea Thompson give excellent performances as well, with good acting and both are able to highlight dialogue with subtle nuances. However, I feel that Mary Stuart's character is the most interesting and emotionally sensitive, enough that she'll bring tears to your eyes. This is an excellent film. It came out at a time when there were a lot of teen movies (Pretty in Pink, The Breakfast Club, etc.), but this is a story that never grows old and is a pleasure to watch again.