That someone would be me.
Welcome to ecomodder.
The Matrix is a pretty good platform for mileage. I've easily been able to achieve a steady 40+ mpg now that its warmer out. If I was the only one driving it I bet 45 wouldn't be too much trouble, but me and the wife both drive the car.
The first thing to check out is driving technique. It not only will provide you with your largest gain in mileage, but its by far the cheapest too! Our list of
100+ ecodriving tips is a great place to pickup some new info. We also have a thread for
ecomodding for beginners which outlines some things you can do as well as modifications you can look into. The first mod I'd look into is pumping your tires up to maximum sidewall pressure. It reduces rolling resistance and increases the life of your tire.
You can also check out the link to my build thread in my signature for some ideas. There are also a few other Matrix/Vibe owners doing some good stuff here too.