While most of the things said above are true, don't let them stop you from enjoying this wonderful piece of film. If you love trains, or just Keaton's incomparable train gags, you'll be enthralled. If you really like Keaton, you'll appreciate the inside joke on his shtick (a rare indulgence on his part). If you think about the stampede scene while watching it, and consider how impossible it is to remake in this day and age, you'll appreciate it more. If you enjoy running gags, you'll find several strings through it. While I admit there are better Keaton efforts, and while I admit I'm very partial, I still say that if you appreciate Keaton at all you'll like this one, too.
Let the comments above warn you that "The General" it isn't, realize that they can't all be five-star classics, and enjoy this really nice film! Not his best, but not bad at all. There's certainly no sense in waiting for his next one (unfortunately). Jackie Chan may still be at it, but all the Keaton we have is all we have--and thank goodness for that much!