How's the tranny shift when its warm? if its fairly smooth then I would change the tranny fluid and that might improve the bang/abrupt shift into drive from park. But if she's slipping even when warm you may have a real problem and should hit the toyota folks to take care of it under warranty (lemon law on used cars)

In general, honda AT's are very rough/aggressive shifting. My 5th gen AT is bangs out of park on cold mornings until it is warm, but if i change the fluid it will be good for awhile...

noel