What can cause hesitation when accelerating from a stop?

What is your question?

This has been a developing problem. At first it only happened when the engine was cold but now it happens on every acceleration from a stop. If I slowly push the throttle, the engine will sputter a bit with little RPM change, then suddenly surge ahead. Punching it doesn't help - acts like it wants to stall. There also seems to be some speed instability when driving at 25-30 MPH. Power is fine at highway speeds, no bucking etc on hills or when passing. No MIL codes. Only thing I've checked so far is the PCV valve - it's good.