The Spider Step feat uses Slow Fall in it's wording, and there is some debate in my group as to whether or not Slow Fall is required to use this feat.
I am of the opinion that the wording implies that you must have a Slow Fall speed in order to benefit from the feat, but a friend of mine disagrees and is of the opinion that even an archetyped Monk without Slow Fall may use the distance he would have possessed if he has not sacrificed that ability. His argument is that the feat is based on the character's Acrobatics and Climb Skills and the wording was used to avoid having to insert a new progression chart.
For reference, I have included the feat below
Spider Step
Your physical mastery grants you an impossible stride.
Prerequisites: Acrobatics 6 ranks, Climb 6 ranks, monk level 6th.
Benefit: As a move action, you can move up to half your slow fall
distance across a wall or ceiling or across ropes, branches, or even
water or other surfaces that cannot support your weight. You must
reach a solid, level surface by the end of your turn or you will fall.
If you have an archetype that gives up Slow Fall, then you don't have slow fall at all, and this feat is useless. You must have slow fall to use it, as you have to have slow fall to have a slow fall speed.
Edit: And I hope there is errata somewhere for Spider step and Cloud Step. A 20th level monk has a slow fall distance of infinite. Half of infinite is still infinite, so a 20th level monk with either feat can move infinite distance with a move action.
If you have an archetype that gives up Slow Fall, then you don't have slow fall at all, and this feat is useless. You must have slow fall to use it, as you have to have slow fall to have a slow fall speed.
Edit: And I hope there is errata somewhere for Spider step and Cloud Step. A 20th level monk has a slow fall distance of infinite. Half of infinite is still infinite, so a 20th level monk with either feat can move infinite distance with a move action.
Try the FAQ.
Seems to be pretty clear that without slow fall the feat is useless. When you sacrifice an ability to get something else you no longer have that ability. Now technically you do not have to have a slow fall speed to take the feat, but without it you can move 0 feet. As a math teacher of mine always stressed 0 is a number. The wording of the feat is that you are able to move up to half of YOUR slow fall speed.
Also the maximum distance is stated to be 50 feet.
If it was meant to work the way your player says it does it would have been worded like this:
"You may move up to half the slow fall distance of a monk of your level"
Seems to be pretty clear that without slow fall the feat is useless. When you sacrifice an ability to get something else you no longer have that ability. Now technically you do not have to have a slow fall speed to take the feat, but without it you can move 0 feet. As a math teacher of mine always stressed 0 is a number. The wording of the feat is that you are able to move up to half of YOUR slow fall speed.
Also the maximum distance is stated to be 50 feet.
The max distance of 50 ft is stated on Cloud Step, where you walk on air, not Spider Step, which has no set limit, so, if you have to know or are planning to use it, just ask your local GM and let them decide or just stick with 50 ft.
The more I look at spider step, it seems to mean that you can move that distance on walls/ceilings but it is a part of your base movement and is not a separate speed that allows to have an infinite speed.