I've recently been learning ColdFusion because of an upcoming project I'm working on ... this is just one small quirk that really irks me.
It's a tag based language, which is fine, ASP.NET uses custom tags for it's controls. The problem is that since all logic goes right in your page (for the most part, I know there are cfc's and whatnot) you are forced to press the enter key to create whitespace because without whitespace, you wouldn't be able to read your code.
Here enters the problem, all of the cf tags get stripped out, and the html is built and sent to the client ... all that whitespace you put into your code now gets sent to the browser as well. Now, you may say that this doesn't break the browser, however, it's adding to your bandwidth. Each one of those line breaks is one more character the user has to download. I usually try to be very careful when outputting dynamic text and try to minimize the whitespace ... expecially within loops.
Anyways, other than that, it hasn't been too bad ... I feel good learning something else that will broaden my skills as a developer.