Yeah, it seems GM doesn't want their new designs tainted with the rental stigma until at least a couple years after introduction. As an ex-Malibu owner of the first generation after nameplate resurrection, I found it especially painful to see the original 1997 design carry on as long as it did. That was a miserable, awful, terrible excuse for a car.
As for the Avenger, I wouldn't be averse to having one as a rental if it had the 283 HP Pentastar V6.

Might not be much tread left on the front tires when they got it back.

I would probably rather have the 200 though, despite being the same car I find the Eminem-mobile just nicer and much more appealing. Chrysler did a great job polishing the Sebring turd with that car.
Anyway, the Impala is a nice car. Haven't driven a newer one, (but have driven the last gen SS that my dad has as a garage queen/road trip car.) The new ones I've just been shuttled around in a few when dealing with vendors at work that had them as rentals. Very quiet and good riding cars. I was a little shocked at the limited leg room in the rear, but that wouldn't be a priority for me personally. I would love to have one with a bench seat, very retro.
Hope you get it back soon.