I use stitch markers and I have to say, it depends on a couple of things, the size of the needle you're using and the type of yarn. I use them a lot when doing projects with intricate patterns in them, just to help me keep track of the pattern and know whether it's time to do a cable or yarn over or switch from knit to purl.
If you find that the stitch markers are causing the pattern to not have the look you desire, the best thing to do is use a piece of waste yarn, make a slip knot and use that as your stitch marker, passing it over from left to right needle as you would a slip stitch. If you do that it does not get included in the work.
Also, some patterns require you to leave a marker in the work so that you can measure from that mark. In those cases I use a piece of waste yarn, tie it to the row there in a loose knot that I can easily pull off when I'm done. Then I use a traditional marker from there, especially when knitting in the round.