I can't believe nobody has done this yet...
Spider Climb
The subject can climb and travel on vertical surfaces or even traverse ceilings as well as a spider does. The affected creature must have its hands free to climb in this manner. The subject gains a climb speed of 20 feet; furthermore, it need not make Climb checks to traverse a vertical or horizontal surface (even upside down). A spider climbing creature retains its Dexterity bonus to Armor Class (if any) while climbing, and opponents get no special bonus to their attacks against it. It cannot, however, use the run action while climbing.
MarkB said:
You are, quite clearly, climbing, and the obvious question here is "If spider climb eliminates the need for any Climb checks, why does the spell bother giving you a +8 bonus to Climb checks?"
Spiderclimb gives a +8 to Climb for things that are not a "vertical or horizontal surface (even upside down)". So what do adventurers use Climb checks for that arn't vertical or horizontal surfaces?
Rope comes to mind.
If you're traversing a vertical or horizontal surface, you don't need to make climb checks.
Climb Skill
Any time you take damage while climbing, make a Climb check against the DC of the slope or wall.
Spiderclimb eliminates the need for a check when traversing a vertical or horizontal surface: the DC is eliminated; the DC remains the same for when you take damage: this DC should also be eliminated.
If you are climbing a rope and get hit while
Spiderclimbing, then you make a Climb check against the DC, and you get a happy +8 bonus on that check.