It does tell you about blown highlights and even more. In the Develop module, there are two small boxes on the upper corners of the histogram. The top left box will tell you when you've lost shadow detail and the upper right will tell tell you when you've lost highlight detail - even as you adjust exposure after the fact. When these boxes are clicked, parts of the image with issues will be highlighted with one color for shadow issues and another color for highlight issues.
Oh, and by the way for those of you who are in school OR have kids in school. The education store of Adobe has lightroom for $99. I just ordered it with my son's transcript as proof and for $99, you can't beat it's features.
"The girlshapedlovedrug messes with my mind." Gomez (the band)