After all the talk about delta updates in the keynote I had hoped that Time Machine would be doing file deltas now. A read through the Lion features page doesn't turn anything up. Anyone know?
Time Machine has always done deltas (unless I have no idea what you're talking about?)
No, it has hard links to already backed up files, but individual files are not stored as deltas. If you have a big file that changes often, say 4 GB virtual machine image, Time Machine will just copy it every time.