Actually my '03 manual did get much better mileage, I thought they did something, my mechanic said maybe they added California smog stuff that may have decreased the mileage. Also when i did mileage on my 03 my commute was longer, going places was a touch further, with a bit less lights and elevation change was a touch less to the local places, even though they were further. So One thing could be that I am closer to everything now, including work, and the part where there is traffic is this part closer into the city where I am now. The Element doesn't have time to warm up and become efficient with the shorter drives and then add to that the manual transmission on the 03 and there is maybe 3 mpg-i guess.
For instance, I am running over to the market now, it is .3 miles according to my gps, my mileage will be lucky to get over 13 because the car won't even warm up. I took about the same trip earlier with to get coffee with my daughter. This morning I checked the surf, a mile and a half each way. My main commute in the morning is in traffic, and on the way home on the empty freeway, I make up all my mileage according to the SG, it is up well over 20mpg.
So more than driving styles, i really think it is your environment that will dictate your mileage. My next test is on the next tank I am going to drive normally with traffic except for avoiding any hard stops, doing a little coasting but not going crazy with it to eeek out every ounce of gas. I want to see what just normal driving with a bit of conservation will get me, hopefully over 16 but I'm not so sure.