Transmission issues ?

[Hvacdude]

So, I've owned my '03 X5 {110k miles} for 2 or 3 months now and I have starting to notice some transmission peculiarities. Twice now, after the car has not been driven for a few days, when I first take off {put it into drive} the trans will slip for just a few seconds. Today I noticed that when I am driving it, it seems to rev quickly but doesn't speed up as quickly as it should. I do not feel any jerking, but it seems like the car should be going faster for the rpm's the engine is putting out. I have also noticed the trans will, sometimes, not shift until the rev's are almost to red line under moderate acceleration. I find my self backing off the gas because I am noticing the "late" shifting. Today was hot {90f}. I was running the A/C. The engine revs {tach} seemed to go up quickly but the car did not pick up speed in proportion to the engine speed. I don't feel any hard shifting but it seems like its not shifting right. I can shift it by the gas pedal: back off on the throttle a little bit till it shifts then give it more gas and it seems okay. It's like the shift is delayed. The car doesn't "buck", but it doesn't feel "right". Any suggestions ? Change the fluid ? Check the level ? no signs of any leak. Rear diff has a little wet looking spot around fill plug, but no stain on the driveway. No wet spots on the drive train under the car. Rear diff oil stain could be from checking the fluid level at one time. I see thru my internet surfing a whole lot of transmission woes with the e53. Mostly hard down shifts. Mine seems to have up shift issues. Any advice from you folks would be greatly appreciated. Thanks for your input.