Looking over the posts so far, here is a collected summary of the differences between the base 13" MBP vs the base 13" MB. For 200 dollars more, you get:
- Illuminated Keyboard
- FW800 port
- Crack resistant aluminum case
- SD card slot
- 4 GB of RAM instead of 2GB on the MB
- Separate Audio In and Audio Out/Headphone jacks (this has generally been overlooked so far, but is crucial if you want to use both headphones and audio out at the same time, or just don't like switching between them a lot)
- Battery level indicator
- Slightly less weight
- Slightly smaller in all dimensions
Both have about the same battery life. Only thing in favor of the MB is that Wi-fi reception may be better with the polycarbonate case. Other than that, it's really a no-brainer that the MBP is the much better deal. I'm sure Apple knows that and would be happy for most people to go for the MBP.
The real problem here is that the MB is $100 or so too expensive. If the same base model were $899, it would differentiate itself much better and would look more reasonable in relation to the MBP.