Personally, I own a Honda Civic Hybride 2006 since february 3rd.
Since then, I went thru 7 tanks for 5,303.7km with a lifetime average so far of 5.2L/100km.
Most of my driving is done 5 days a week during rush our. (26km commute)
Tank# --- L/100km
1 5.9
2 5.8
3 5.4
4 5.0
5 5.3
6 4.8
7 4.5
Here is a pic of my last tank.
In addition, 178 owner can't be wrong. (Source: GREENHYBRID.COM)
I put pictures because unless you are a member, you'll see US MPG values as oppose in L/100km.
I just want to point out here that if you are carefull in the way you drive, you can get EPA number like with any other cars.
Keep in mind that this car in not 1 year old so the average L/100km will go down along the summer.