For example, If I have a walk cycle IPO, nicely extended as cyclic, can I have a character walk for 100 frames, then TURN OFF the IPO, or jump to a different IPO and just stand for 100 frames before going back to the original IPO to walk off?
I know it’s possible to assign an IPO for the Game Engine, but was wondering if something similar could be done in a straight anim.
(I’ll even plunge into Python if I have to!)
I’m just learning to use the IPO Curve Editor myself, but perhaps some of the things I have learned may be of use to you.
I have learned that you can easily and instantly change the camera position to make it appear that you have switched to a new camera (locrot key camera, change frames, move camera, locrot key again, change ipo curve to constant).
I have learned that you can easily change an animation from the 3D window by using dupliframes, and selecting a key in the ipo window. The corresponding dupliframe in the 3d window will become highlighted. You can then grab and move it, simultaneously changing the values for that key in the ipo window (I thought that one was really cool).
I also copy several keys and move them (again, the grab command) to the end, essentially creating new keys. This is quite useful for duplicating an action. I’m sure this can also be easily done in the Action window, but I haven’t figured that beast out yet.
GreyBeard’s Video Tutorials has a great video tutorial on using keyframes and the ipo curve editor. You might want to give that a try.
Don’t know how much help I’ve given you, but I tried. 
I appreciate the answer DYeater. What I’m after is a little outside that though…
An object can have an IPO assigned to it. In fact, the same IPO can be assigned to different objects by selecting a different one in the IPO Editor window.
Is it possible to change the IPO being used by an object ON THE FLY!
(So in my example above, a walkcycle IPO can be applied to a particular object at a given frame)
The “no” answer to my question would be that an object is stuck with the same IPOs it is given throughout the animation.
that sounds like something you would use actions and the NLA for. I don’t think you can do that with just IPO’s
dont ask me how though as I haven’t touched the NLA yet
correct, you would have to use the action editor and the NLA editor [and they work on armatures, not ojbects… although each bone has an ipo block I doubt that is what the poster was tweaking]