Slowly but surely, hard drives with 4 KB sectors are replacing the "legacy" 512 byte sector size. By January 2011, all drive vendors will have made this transition. Buyers of new PCs are safe, but there are still a few performance pitfalls to note.
The new 750 GB drive clearly outperforms the 640 GB model. However, this has probably little to do with the sector size change, which becomes more visible in other benchmarks.
Stay On the Cutting Edge: Get the Tom's Hardware Newsletter
Get Tom's Hardware's best news and in-depth reviews, straight to your inbox.