I disagree with this, I like how it is right now. For certain kinds of code I need things like FlexibleInstances that I absolutely wouldn't want enabled everywhere. As it currently stands in Haskell I can turn it on only in the files that need it and it doesn't leak to the rest of the program. And having them at the top lets me know ahead of time that things I would normally view as syntax errors are in effect for this file.

The biggest complaints I see people make about Haskell are language extention lines and imports but for me these are both IDE issues. I'm not aware of many readable languages that end up with lots of imports for any non-trivial code.