Better late than never...replying this post I mean.
For me, I started out with JPEG only for a year and a half (this is my third year having a DSLR, let alone a D40). I know that JPEG is tougher to fix errors (mostly my errors) and that's the primary reason for me to shoot in JPEG. This is especially good if I'm a beginner. This way, I force myself to do everything right the first time. Being a beginner and using JPEG, I tend to observe my mistakes more accurately than my friend (also a photography buddy - he's having a D80). I tend to be more aware of my shots more often and so I improve my shots that way(at least I believe I did).
Now, I switched to RAW, and tend to edit it more often. Yes, my photographs looked better through editing but I wouldn't have to drag from the mud if I didn't get it as much right as I did the first time. The primary reason for me to switch to RAW is because of White Balance. Other than small amounts of touch-ups (whitening of teeth, removing dusts, straightening of horizons, etc), exposure-wise, I tend to think "JPEG". That would help me in discovering how my camera, built-in meter and different lenses behave in different lighting environment.