Be careful about recording lectures without the express permission of the professor. The lecture and any accompanying material is the intellectual property of the professor and is protected by copyright law. While most profs will probably not have a problem with recordings for personal use, some may have concerns with you sharing them. Just something to keep in mind. If you are worried, just drop in to the profs office hours or catch them before or after class and ask.
Very good warning, considering he said nothing about recording, nor sharing lectures. But hey, thanks for informing us of your intellectual property rights, professor pants too tight.