I will use either a packing folder or a similar size packing cube for my "main" clothes depending on the type of trip. I use smaller packing cubes for everything else. Easier to see what you have, easier to get through security (since most of my cubes are either completely transparent or are see-thru on one side), and together they weigh about one pound (excluding the main folder/cube)
I use a TB Tri-Star and can fit everything I need in it with room to spare. With my netbook-sized daybag inside, the whole things weighs in around 16 lbs. Add about 3 lbs if I bring the netbook and power cord.
And I don't double up on shirts in the folder or packing cube. I just fold them gently and pack each shirt opposite (one shirt collar to my left and pointing up, next shirt collar to my right and pointing down.)
I've actually found that using a packing cube the size of a folder and making sure it is kept in place by internal straps sometimes causes less wrinkles than a folder.
The final secret--a travel sized bottle of Downy Wrinkle Release. I used to travel with a portable steamer but it was too heavy. The Downy works well.