Believe me, it teaches you everything that a digital camera never will. Don't get me wrong; I am a huge fan of DSLRs and Photoshop but I admit that I would never learn to compose a photograph if it weren't for a film camera.
Using a DSLR and Photoshop (or other software) allows you not to think during the process of making photographs. You know that if you take a photo and it is not going to look right you're just going to delete it or, if easy enough, correct it in Photoshop. Underexposed/overexposed? Not a problem, I'll just use highlights/shadows option and voila la... Something got in your frame? This is easy; crop it/erase it/ clone it. You don't have to worry about agitation marks, dirty lens or crooked horizon... everything is fixable. And if you really want to save your time just re-shoot the frame as many times as you want. You can preview the picture, delete it if it looks wrong and take one again. I have to admit that this is the beauty of digital photography. You see your results immediately, you don't have to stress about blank frames showing up, and you are able to edit the photographs as soon as you get to your computer.
That easiness makes digital photographers become less aware of the essential part of photography - picture design.
I believe a firm education and plenty of practice with a film camera is essential for every amateur and professional photographer. It teaches you patience, but also makes you pay attention to every detail including proper exposure and framing. It is hard to re-shoot an unwanted photograph if you don't really know what you have in the first place! :) This is why you have to think ahead, spend some time on composition, remove the unwanted objects from the frame before pressing the shutter to get rid of/lessen the headache during printing.
I have two different styles of photographing with film and digital. With film I try to be precise, slow, patient, neat... I like to take my time. With digital I am sloppy, my lens is dirty but I don't care... I know I can easily get rid of it. With film I am able to make about twenty decent prints out of a 36 roll but with digital I can only get about fifteen out of 100. See the difference?
Today I was walking from school and I was able to look at random stuff and frame the picture in my head and make it look out of ordinary. I don't think I would do it if I had never worked with a film camera... or maybe I finally start to dig photography? :)