It could be that the ECU simply needs to "relearn" everything. Try driving the car around for a couple days and see if the problems clear up; it normally takes a couple of good driving cycles for the ECU to really settle back in. Also, did you clean the cable terminals before putting the new battery in? I've seen some very strange things happen to cars because of a loose or dirty battery connection that 2 minutes with a wire brush fixed right up.
Is the car throwing any sort of check engine code? If so, Advance Auto or Auto Zone can scan those for free and give you the numerical DTC code (if they tell you what you need to replace, ask them what the actual DTC code is - something like P0134, etc), and you can check a couple of different places online to see what that DTC code is related to.
As far as the "idle control sensor", I poked around a bit and couldn't find anything other than the standard idle air control valve (unfortunately, still expensive at $230). Is it the I4 or V6 Camry?
I recently replaced my car battery. After I started up the car for the first time the engine seemed to be struggling to idle. It was pulsating between <200 RPM and about 500 RPM. So I immediately decided to take it to a repair shop and pulled out of my drive way. On the way out the engine completely stalled, and then it completely stalled at every red light I hit on the way to the shop. Had to restart the car each time.
The mechanics told me it was the "idle control sensor" which needed to be replaced and since it's next to impossible to find just an idle control sensor for my '03 Toyota Camry they said it would cost about $900 to replace the whole throttle body.
I ended up just leaving and driving the car around for a few miles and then the car stopped stalling: idling steadily at about 500RPM. Still not optimal since I seem to recall it idling at just shy of 1K RPM before I replaced the battery. So do you think it will return to that level eventually or does idling steady at 500RPM even after about 30 mi. of driving seem like a bigger problem?
My amp funds are at stake!