I have tried few code formatters and almost always regretted it. The big problem is that code formatting contains a significant portion of intent and explanation. Sometimes I want to put two assignments on same line because it emphasizes relationship and atomicity but other times it's better to keep them on separate lines for sparcity. There are actually quite a few times I wanted a line go well beyond 80 chars because I wanted to de-emphasize unimportant monotonous part taking away all attention and have far more more important steps immediately stand out to reader. I take code formatting very seriously and consider an integral part of my expression. Style guides are good but they shouldn't be followed like a robot, let alone enforced by robot. In fact code formatting tells a lot about culture and philosophy of an author. For example K&R C starts braces on same line to emphasis compactness as elegance, C# doesn't to emphasize sparse code as elegance. In SQL sometime it's great to put subquery on same line and sometime it doesn't - it really depends on what you want to emphasize and convey rather than hard and fast rules on number of tokens and syntax analysis. Code formatting is not just set of fixed rules, it's a communication mechanism that guides reader on what to focus, what is unimportant, where is a gasoline spill and where wild fires may burn. This is not to say everyone takes their formatting seriously which is where automate formatter would probably add value (and the case where you are importing/copy pasting from somewhere else). I think K&R C is likely the gold standard for code formatting. You should try out your formatter on those snippets ;).
It's funny, I hold exactly the opposite view for exactly the same reason! I regard a code formatter nowadays as an essential tool for programming productivity, the fourth most important tool after an editor, compiler and web browser. The reason is that the limit on how much I can get done is not so much wall clock time as mental energy. The thing that costs mental energy is making design decisions. Without a code formatter, every few lines provides another invitation to make a design decision about layout.
That's all fine if you are the only person who will be touching that file. The problem is that most of the time a piece of code will have multiple developers working on it over time. Each dev will have a different perspective of what that intent and explanation should be.
I have wasted far too much of my life arguing with people about how code should be formatted. Ideally I would just have a rule set up in source control to format the code on checkin and be done with it.. Then if I want a different style when I come to edit a file I can run whatever formatter I want on it and it won't affect anyone else.
