Think of it like this: You have your decorative edge with the slipped stitch and then your pattern starts, so it doesn't affect the pattern at all.
Oh, and if the pattern calls for a knit stitch as the first one, slip it knitwise. If the pattern calls for a purl stitch as the first stitch, slip it purlwise.
Just because a pattern tells you to slip the first stitch, you don't have to. If you decide not to slip the stitch, be sure that when you do the first two stitches of a row to tug on them a little more than you normally do to tighten them up.
But by all means, experiment and see how you like both methods. That's the only way you're going to decide which one you like (no matter what we tell you here).