Most of the upgrades to the civilian bands are for faster first fixes and making it so a fix is consistently more accurate. Also the ionosphere can be directly measured by your gps receiver, so fixes will be more accurate.

They are doing this because many civilian applications have emerged that need a more accurate signal (one is turn-by-turn navigation). When GPS was first developed, it was first envisioned as outputting coordinates and you looked up your location on a paper map, where 2m was better than most maps you could get.

The military is getting the ability to get a signal that is 100x more powerful in a small area.

It will be awhile before we see receivers using the new signal as the first of the new GPS sats launched today (some of the old ones are broadcasting the new signal, but not enough of them)