My analysis of the skills below is my interpretation of their utility. Discussion is welcome. There are many more solutions then the ones I outline. Please leave your own suggestions in the comments.
Acrobatics is a skill reflecting physical ability and agility. It uses the dexterity stat as a modifier.
What can you do with Acrobatics?
Balance: Any situation in which you wish to balance on a surface less than 2" in width has a DC 20. 1" width is DC 40, Hair-thin is DC 60, Liquid or any surface incapable of supporting a characters weight is DC 90, and standing on condensed water vapor (clouds) is DC 120
Jump: For each success, you can jump 1 foot horizontally with a running start of at least 10'. You need 4 successes for each vertical foot. (from our previous example, of an acrobatics skill of 37, this means that on the mythical average roll, a level 15 character can jump nearly 50', or 13' straight up.)Increased land speed gives a bonus of +4 per 10' over 30, meaning a 15th level monk has a +20 to this check from land speed, meaning his average roll is nearly 70! (allowing him to jump 67' horizontally, or 17' straight up vertically).
Reducing the impact of a fall: A DC 15 check will allow you to ignore the first 10' of falling damage on a deliberate fall.
And Tumble: This is an ability to allow you to get past an opponent without taking a free attack.
Which of these have ground for use?
The answer to this question for many of these has a lot to do with what type of game you want to run. If you like superhero games or fantasy characters with superhuman powers, then the balance and jump categories fit right in.
Historically, this is one of the easiest skills to buff, meaning that anyone that decides to focus on this skill can start to achieve really impressive numbers quickly. Is that such a bad thing? Not really for a pathfinder game - little will be broken by the monk being able to jump fifty feet or so at level 10.
Balance: Balance skills are bad game design. They are made as part of another action with the penalty of "you lose your turn". It is not a particularly fun activity to sit around a table and roll to see if you get a turn.
It is used under a time constraint and you cannot model it at the table, but the result of 'lose your turn' is less a serious consequence and more something crappy that happens and there is no conflict with another entity.
A better solution would be just to apply the "you move at half speed and lose your dexterity bonus to armor class while balancing", with a requirement of needing to not be wearing heavy armor. This keeps the same flavor without requiring tedious rolling and missing your turn.
As much fun as it is for DM's to make players not get to play the game - it is somewhat unfun for the participants.
Jump: A commoner of average dexterity can make a running leap on a flat surface and jump either just 1' or 20'. Though this technically fits within human norms (an average long jump is 12', Olympians can reach double that with intensive training), it is far too much variance. Also, this type of activity requires years of special focused training to reach a distance of 24' - a distance possible for your first level rogue.
I do believe that these types of leaps are very much the type of supernatural ability that monks should exhibit, so I think total elimination of jumping is a bad idea. This is an example of a skills where the variance on the d20 roll is much too high to model any sort of jumping consistency. The original 3e check was much more realistic but more complicated (Distance was 5 ft. + 1 ft. per 1 point above 10.) If you were to perform a series of long jumps, they would all be within a few feet of one another.
I have a hard time not simply allowing players in light armor to make any jump less than 15' or so even if they have to catch the other side and pull themselves up. I would simply allow monks to jump much farther. In a combat situation I'd set a default range and anything at that range to 5' farther I'd require some sort of pass/fail dexterity check. This solution is perferable to me, because I don't want level 9 characters able to jump 30'+.
The biggest issue with the jump skill is the 'time constraints'.
In nearly every non-time constrained situation there is another way around the situation making this skill useless.
Jumping does hit two of the points, damage is a serious consequence, and it can't be modeled at the table. This is the only check with a partial result for a success. Which means that interesting situations can occur at the table, but frequently don't.
Reducing the impact of a fall: This is another thing that seems like a class feature; it doesn't increase with distance or level. Making this a class feature of the rogue or monk seems the simplest route.
Tumbling past an opponent: Here is where there is some ground for a skill. This has time constraints, puts you in conflict with another entity, has a serious consequence for failure, and can't be modeled at the table. It is also something that comes up quite a bit in play.
Pathfinder has a really excellent innovation for this, the combat maneuver check. The key part of this is the maneuver defense. In older games allowing a normal melee attack at this combat maneuver defense to avoid getting hit seems like a good solution. Anyone who wishes to focus in these techniques could use their level instead of their attack bonus (thieves, et. al.)
What is it we gain by having this skill?
That's really the question I'm addressing here - how often does it come up, how important is it to what is going on at the table, how big a difference does it make to the actual enjoyment of the players.
The only part of it that comes up every session with any regularity is the tumbling part. If you're buying into the rest of the d20 skills system, then tacking acrobatics on isn't a complete waste of time, but the skill is not necessary for adjudication of these situations.
What do we lose?
Acrobatics is one of the worst offenders at skill hiccuping. These rolls often have little drama and they are called for far too often. Often it is best to avoid using the skill at all due to the high variance of the results. The consequences are a hideous trifecta of not very severe, uninteresting and unfun.
Conclusions & Suggestions:
- Balance on any reasonable surface (1"+) in light armor, move at half speed and get no dexterity bonus to armor
- Jump auto success on jumps less than 15', dexterity check to succeed at jumps between 15' and 20'
- Monks and Rogues can reduce falling damage
- Use an attack check versus hit dice + 10* to avoid an attack when doing something that will cause you to be hit. Allow training to have the attack check be equal to level instead. *(either BAB+strength bonus to hit vs. HD+10, or melee ThAC0 vs AC 10-HD, feel free to modify by size or circumstance)