is it ok to run 20's in winter? yes.
is it ok to run the summer performance tires that come with the 20's in winter? no.
well, i mean, you can, but i wouldn't call it safe. either get all seasons or get a dedicated winter set. summer tires when it's cold are bad. summer tires when it's cold and wet, as snow/ice will do in new york winters, are just asking for an accident

Has anyone ever had success getting the dealer to swap out the summer 20's for all-weather 20's before taking the vehicle? Mine won't be ready until July so I have some time.

Negotiations, Negotiations, Negotiations — you should still have time.

Tire “swaps” are easier than wheel swaps as wheel swaps change the build sheet if the dealers do them whereas tire swaps are not considered “changing the build sheet” in the same way as wheel swaps are.

— John

No, I really didn't. I took delivery in the winter time and the car came with summer tires on it, so I had a decision to make (I didn't think to negotiate it at the time). I jumped from a RWD Dodge Charger with A/S to what I would consider a premium AWD car. I figured that with A/S tires I'd be sacrificing performance in the summer months, and safety and traction in the winter months.

I perform the seasonal wheel switch over myself on my Audi as well as two other 4 wheel setups. It is definitely a painful task, but with a impact driver, a floor jack, and having switched from the stock Audi lug bolts/plastic caps to Gorilla Locks it's less painful.

I hope this helps you in your decision.

Thanks- you all have been incredibly helpful. My latest thinking is ill take the car as-is and invest in a pair of winter tires for the same rims. I'm leasing it so not sure it makes the most financial sense but I have a few more months to figure it out. I think the $1000 or so is worth the peace of mind on my first ever performance automobile.

The fact that you're leasing makes more sense in not buying a winter setup. I own and plan on having the car for 10 -12 years, so investing in a winter setup does make sense.
Though, here's a used RS5 winter wheel/tire set w/TPMS; less than 2k miles on set that's asking for $1,000.

Bigpoppaco is buying an S5 - that winter set you linked is using a wheel with a 25 ET (offset), and also a 255/40R19 tyre (not a 35 series). There may be a clearance issue on an S5, and he won't have individual TPMS. Apart from that, it is an attractive offer - the Sottozero Series II (240) are excellent high performance winter tyres, and were the original homologated winter tyre for the B9 RS5.

I'm actually leasing it unless something dramatic happens between now and July when the car comes in.

Sure, I was more commenting on the (un)suitability of those wheels for an S5, vs an RS5.

I change tyres each season, using the same wheels, on both our S5's. Whilst Nikon1's warning on wheel or tyre damage is worth considering, I have never had an issue. Just go somewhere reputable.

I usually keep my cars for many years so it makes more financial sense for me to keep two sets of wheels and tires. With a lease vehicle or if I was someone who jumped from car to car, doing what Glisse does makes more sense. But in either case, the suggestion of “go somewhere reputable” is top on the list.

— John