I just imaged my C partition a couple of days ago using Ghost 2003. The image fit on two single layer DVDs. IMO optical media is more dependable. After all one of the main reasons for imaging in the first place is in case of drive failure.
Of course if the OP has only one partition with everything one it then it would take quite a few disks. Take image I created was for 12.5GB and it fit in 8.8GB (2DVDs).
So you can expect 40/50% compession using default settings. Of course backing up files that are already compressed, like jpg & mp3 aren't going to compress much. Basically you only pickup the slack space due to unfilled clusters.
Acronis is excellent and is well priced right now at newegg.com.