Let's face it, Whips suck. There are only three reasons to use a whip:
1. Role-playing. 2. Looks. 3. To disarm opponents.
The first two, while nice and good, normally ends with a PC switching to a useful weapon when in real combat. Disarming opponents... ha.
To even get the ability to use a whip, you have to take the Exotic Weapon's feat. If you wanted to disarm opponents, you could have just taken the disarm feat, and disarmed them with -any- weapon.
Did I mention whips also can't be wielded in the off-hand and their damage is 1d2?
Yeah, they suck bad.
However, I do have a useful suggestion. Give whips the ability to stun people for one round a percentage amount of the time if they fail their save (reflex save preferably). It makes sense and makes them useful.
This meshes well with their mechanical and role-play usefulness. By allowing a whip to stun people, it symbolizes a few things: 1. A whips blows, while not deadly, HURT. Being struck by a whip is going to leave you stunned for a few seconds in pain.
2. The sight of a whip being used against you, if you were a former slave, is bound to bring back painful memories.
3. A whip wrapped around a leg makes it difficult to escape, to run away.
4. A whip around the wrist makes it difficult to swing a sword.
5. A whip striking you is certainly enough to interrupt your concentration while casting a spell.
Some of this is simulated with the disarm feat, allowing you to wrap the whip around someones weapon and disarm them. The stunning effect is the logical extension of that idea. Being a colony of former slaves, who were most likely whipped, it would be nice to see the weapon being used more often and the in character reactions to seeing it.