Perfect Wavelanding is performed by air dodging completely horizontally JUST above the ground. It's easier with certain characters than others (Ganondorf's is pretty easy), and some characters can't do it at all. Bowser's perfect waveland seems to be a 1 or 2 frame window, so it's possible to get pretty consistent with practice. You can also perfect waveland onto platforms either from above or below. A quick note: you cannot perform a perfect waveland immediately after you jump like you can perform a wavedash.
Perfect wavelanding is deemed such because it yields the maximum distance possible from a waveland. This means you can more effectively approach opponents than with wavedashing. Since 3.5 is still pretty new, most people don't expect Bowser to have such good burst movement, and wavelanding can thus catch your opponent off guard if used intelligently. Offensive options out of perfect wavelands include Forward Tilt, Jab, Down Tilt, Grab, or jumping and using an aerial. Defensive options should also be considered; shielding immediately after a waveland towards your opponent can be used to bait out a reaction that leaves them in a disadvantageous position. You can also waveland backwards to mix it up.
Overall, it's definitely worth practicing if you want to play Bowser at a medium to high level of skill. This character has been sorely lacking movement options since his Melee debut. With the addition of a practical and safe movement option, Bowser has gained significantly more potential to be viable, even good, in competitive play.
