You don't have to watch the two videos after the break if you don't want to -- we'll just tell you that Italy's iSpazio blog tested the white iPhone's proximity sensor and "death grip" antenna seam issue, and that, surprise, they're both fine. The proximity sensor seems to work a little better than that on my black iPhone 4 (based on observations of this video), and while the "death grip" on the iPhone 4's antenna does make it lose a bar, reception is unaffected. So don't worry.
The bigger question is why the white iPhone 4 took so long to arrive. We've heard Apple was working to improve the proximity sensor and antenna. Also, there may have been issues with the camera, or perhaps Apple had trouble nailing the perfect shade of white. There are a few improvements here, but (without having actually seen one myself) there's nothing that would conceivably cause a 10-month delay. Maybe it really was that shade of white -- was that worth 10 extra months?