Jump caps at 40. To the best of my knowledge, this is/always has been the case, and is assumed here.
Based upon that cap, many people advocate a very small allocation of points into jump. Namely, enough that, with the jump spell, you will hit that cap of 40.
A different point of view, especially for those of us in too much of a hurry to wait around for other party members if we can't self-cast the spell (or even just those that solo a lot), is that frequently you do not have jump. You might have potions or the new clickie; but this is also offset by the amount of mobs that dispel throughout so many of desert+ stages of the game.
One thing I never really qualified until today, is in regards to character acclimation. If I become used to my character moving like X (X being a definitive movement characteristic made up of my striding/jump/tumble/fallingspeed), then the more my reaction time becomes naturalized to the characteristics of X. Therefore, deviations from X are more and more going to cause me to misjudge my reactions, with potentially lethal consequences. For example, Bob might be able to drive your hummer, but it isn't going to handle quite the same as his geometro, and therefore there is an increased room for error resulting.
This is probably most often realized when you go to play a character you haven't played in a while. However, it is important to note the ways to avoid this are available (wearing striding even if you caste haste, having high unbuffed jump, etc), although these are always to be balanced in regards to other character considerations, they are of definitive value.
Quantification of this value, therefore, becomes the next step, but probably the hardest. The main reason for this is playstyle. If you are an "twitchy" player, always moving about because you can't stand holding still for even a second, then I would foresee a high correlation between the value of the above and this, and vice versa. Zergers fall into the same boat, since the good ones know exactly when it is time to pull out of a dangerous situation, and when another two or three hits are available, and the microsecond difference could be the difference between living or splattered. Because of the above explanation, there is also some carry-over into solo-ers, however, *some* solo-ers also tend towards the overly patient, single-mob pull type techniques, where this is more irrelevant. There is definitely the possibility of over-generalization there.
So... random thought for the day spent, enjoy your morning.