sometimes changing the automatic tranny fluid helps with shifting... at least for me anyways. i've also used the lucasoil transmission additive with great results. it thickens the fluid up a bit so it works better in extreme conditions where the regular fluid can fail. by thickening up the fluid, it will help bring the pressures back up to spec so you get smooth shifting. similar to getting a thicker oil to keep engine oil pressures up.
but then again, your weird shifting could just be quirky electronics or a sensor gone bad.