Can't speak for the engine, since i went from a 4.4 to a 3.5d.
Power is comparable, but i'd say the 4.4 is more responsive from go.
I like the Pano roof, because my son is still rear facing, and it gives him something to look at, when it's more than just sky. If he's not riding, i normally keep it + the panel close.
Got 3rd row seat, and haven't used it yet. Haven't even tried setting it up, and it's been almost 3 months. It's more one of those "it'll come in handy if we need it" decision.
Handling on the e53 was better imo. but I think it's attributed to my e53 having sports package, and i opted not to get it on the e70. There's some regret.
Otherwise, I like the new gadgets + electronics. no iDrive on my e53. In the 08, you'll have the older version i think. Auto climate, auto lights, programmable/touch sensitve buttons, and they work pretty well too.

My biggest gripe is the storage area. glove box, center console, the way you open them, just didn't seem well thought out. used to have a sunglass holder in the e53 by the rear view. no more on the e70.