Case in point: my friend and smash buddy Brian has a very good Peach, with solid mindgames, top notch recovery, float tricks, great use of the roll and spot-dodge to pwn my ***, excellent mixups, good edgeguarding and good turnips. He doesn't wavedash with her, because he doesn't see the point, and he's not very good at it. Peach vs. Peach I can't beat him at all, even when wavedashing (but my Peach sucks).
At tournaments, he generally goes about 2-2, losing to pretty good players, and as I watched his play, I noticed several spots where he could have WD'd out of shield into a grab, or just barely dodged an attack with a WD, but instead he chose to roll, and gave the opponent the advantage. He's good with the roll and can usually stay safe and pull a hit out of it, but sometimes he gets punished with a combo, and generally loses the match by half a stock or less.
Point is, WD can win you games you would not have won otherwise. You don't have to use it alot, just make sure you know what you're doing.