The fuel drill is a pretty awesome improvement, and I own the compact drill (2601) and the compact hammer drill (2602) and have used the premium hammer drill (2611). The biggest difference is in very heavy use. 4.5" holesaw, hammer mode hole after hole, etc. Compared to all the other Milwaukee, Bosch, and DeWalt drills I've used and own, the heat generation is way way less. More power from the battery to the bit, so longer run times. It also just seems to turn any bit faster.
I use the non fuel circ saw all the time, which was already the best compared to Bosch, Makita and DeWalt, and I hear the new Fuel is way better.
I believe most of the Fuel tools will also include the 4.0 batteries, which is another consideration.