Trip as an action.. many questions.. also, is it worth it to trip an opponnent?

[Stalker0]

While I think trip is powerful, its not godly powerful since the opponent can use either dex or str to counter, and you have big penalties against big or multilegged creatures. However, the ability to take away 3 or 4 attacks from a fighter at high level to just 1 is very nice.

 

[Trine]

Expertise + Improved Trip is a great feat chain (all two of them) to follow if you can. Against some opponents, trips are nearly impossible. Against others though, you can prevent a full-attack against you while still getting your full-attacks.