I don't know why there has not been any responses yet. Last semester I also wondered about recording apps and downloaded a couple. In the end I used the voice memo app on my IPOD touch that we were required to purchase. Worked pretty good. Don't know what other features I would have wanted and it was fairly sensitive as well.
I bring my netbook into class, and use the recording within OneNote to record lectures - it's awesome because the recording sync's with the notes I type, so I can click anywhere in the notes and it will playback from that point in the lecture. OneNote came bundled with my computer, in Microsoft Office - it sync's online (with microsoft's skydrive) and my droid with the onenote app. I love it!
I've used iTalk Recorder before and it's worked pretty well for recording lectures. It's free but if you want to upload your recordings to Dropbox you need the premium version of the app which I think costs $1.99. This way you can share recordings with others if you wish!