I changed my transmission fluid on my Malibu at 100k miles.  I do drive in hot summers (Riverside, CA) and heavy traffic (OC commute) and my transmission isn't roasted.  The dealership does suggest not to flush the transmission, just the basic service of drop pan, new gasket, filter. Should be about $100.  
If you do get coolant flush, do not mix dexcool with regular green coolant.  Now I managed to get my hoses to last 100k miles.    
Also, if you have the V6 engine, pay attention to the lower intake gasket.  It is know to be junk and will leak sometime in it's lifetime.
At 100k, you could replace the spark plugs.  I'm still on the original ones from the factory at 108k, no problems at all.    I haven't seen a check engine light ever.