How do I get the sheen even?
Couple things come to mind:


Don't go back to previously painted areas until that area has completely dried.  While the paint is drying it will look splotchy and uneven.  Walk away, don't touch it, and come back in about 4-6 hours when it has dried.  It will then look even.  
Make sure you are putting enough paint on the wall and don't try and stretch a roller too far between loading it with paint.  For example, load up your roller with paint and then put the paint on the wall in a wide "W" shape.  Then roll it out in that general area but don't try and push the paint too far on the wall without going back to the paint tray.
Let the first coat dry thoroughly before putting a second coat on.  If you start putting the second coat on too soon (or come back to an area that started drying but has not dried completely) then you will disturb the first coat and get blotches where the portions of the first coat that began to dry already become pulled up and absorbed by the second coat.  
Roll out an area and then walk away.  Don't keep rolling it out trying to get it perfect.  Just put the paint on nice and even with about 4 to 6 passes with the roller (ok maybe I do more like 10 to 12) and then move onto the next area of the wall.  Rolling the same area out over and over again just makes the coat of paint very thin and also you can end up pushing any dried areas of paint around the wall.