Summer Interlude is Bergman Beta, a rough approximation of the deeply spiritual and personal films the director would make later in the 50s and throughout the rest of his career. But that's not to say that the film isn't successful on its own merits. The story, which surrounds an aging ballet dancer and the love affair she had when she was a teenager, is simple but moving. There are certainly a lot of brief sketches of emotion that rely on long-standing film cliches to stand in for genuine emotion (as can be the case with any young filmmaker) but Bergman was beginning to come into his own as a director, and consequently the camera's gentle but confident presence shows a maturity somewhat lacking in the writing.
The most obvious comparison between Summer Interlude and Bergman's later, well-known work is Wild Strawberries. Both films focus on people reflecting on their past life and love, though of course Marie is at the end of her career rather than the end of her life. There's even a literal connection to the later film's title, as the two lovers in this film first begin to fall for each other over a field of wild strawberries. But the emotional pull her is less compelling, and the influence of Hollywood melodrama on Bergman's technique is still very apparent here, especially when compared to a film like Wild Strawberries, which seems so unique and even revolutionary. There's a hint of the "absence of God" theme of Bergman's later work towards the end of Summer Interlude, but it seems more specific to the moment than tied to the thematic thrust of the film as a whole.
After all, Bergman's clear goal here is to entertain, something that was always at the forefront of his films but seems much more obvious here - especially with the early humor in the film and the sweeping score. It's something often forgotten about many of the directors now considered "serious" or "intellectual" (Bergman, Fellini, and Truffaut in particular do not hold up to this rejection). It's what makes early work like this so important for understanding a career as a whole. When it's also enjoyable on its own, that's the icing on the cake.