It really depends on how you knit, however, the one thing I have noticed is that it really does all come out in the wash.
Last year, when I was really unhappy with my combined knitting stitches I realized that things equallized once I had washed a project and the fibers loosened up some, but it wasn't exactly what I wanted, so I switched up to Eastern Knitting and got the conformity of stitches I wanted.
If you're a Continental knitter, you may be doing something during the purl stitch that is twisting your stitches and getting them to lean in a way you don't intend. Watch the videos here on beginning techniques and see if you're doing things right. They were a huge help to me.