Certainly, the best reason to watch "It Happened Tomorrow" is that it is fun to watch, with an interesting premise, a story and characters that are pleasantly exaggerated to just the right degree, and a good pace that keeps things moving. But it's not without a point, either, and by keeping things from ever getting too serious, it's rather effective in its implied observations.
The likable Dick Powell and the appealing Linda Darnell work well together, giving solid performances without trying to get more out of their characters than they should. Jack Oakie is nicely cast as the boorish uncle of Darnell's character, and he gets some very good moments.
The premise of reading tomorrow's news is certainly familiar in other forms and from other pictures, but it is the kind of interesting idea that always works well when it is in good hands. René Clair has the right feel for it, keeping things light most of the time, and adding some creative details. The story is often very clever in showing the ways that the advance knowledge both influences and misleads the characters.
The story moves fairly quickly, with some good period detail. It's an enjoyable movie and also, without being heavy-handed or obtrusive, illustrates some worthwhile ideas.