There's many changes to the casing actually. 3000 compared to 2000:
- The edges are more curved (may be more comfortable)
- The area in the middle of the face buttons and dpad is more concave
- Speaker holes are a little smaller/sharper edges
- Extra microphone hole
- Sony logo has flipped sides
- 'PS' PlayStation family logo has gone from the top corner to replace the 'HOME' button label of previous models, bringing button labeling in-line with the PLAYSTATION 3
- All buttons under the screen are now lozenge-shaped
- Thinner silver ring on back of UMD drive door with different finish
And there may be even more subtle differences.