Codec and video settings REALLY MATTER when making videos.
I do use a headset and pretty much always have for recording. Cam studio is really hard to use without divx codec and settings.
If you are super adventurous, you can look into FFMPEG (what I currently use under linux, though it is cross-platform). FRAPS costs money but does very well with loss-less recording which creates best quality but huge files you'll probably need to compress (FFMPEG can do lossless also).
I will release a guide to how I do things on linux these days soon.
It took me a long time to understand what a lot of the video recording settings do, and even now I don't understand it all.