From a designer's perspective, I think it's more important to consider major adjustments to the jump mechanic, rather than focusing on minor adjustments to height, speed, landing style, etc. Double-jumps, Samus' midair-hover, wall-jumps, and the like, all add a lot more value and interest to the overall design, rather than tweaking a standard jump to make it "perfect".
Sure, tweaking is important, but that can be done by getting feedback from players, and adjusting gradually. If you want to make a game with awesome jumps, focus on a big change to the jumping that makes it completely different and offers new ways to play.
Double-jumping, for example, is awesome - it offers a whole load of possibilities for how you play. It also allows you a second chance if you mess up, making it less demanding on the player, and allowing the designer to focus on more interesting challenges.
When it comes to these kinds of design decisions, I say it's best to think of big changes, rather than detailed tweaks. Just my two cents, and the way I like to design, so feel free to disagree