Clerics are treated with some caution on the planes. Most planars figure that clerics, so close to their respective deities, must have special powers. This isn't necessarily true, but it's still a tough feeling to shake. Nevertheless, clerics tend to attract trouble from planes of contrasting alignment. For instance, fiends love to give good-aligned clerics all kinds of grief.
Clerics who focus on the planes trade their ability to turn Undead for control over extraplanar creatures. Outsiders view skilled planar clerics with awe or fear.
Planescape Campaign Setting, A Player's Guide to the Planes, page 13
Planar Handbook, page 30