Quite impressive! Are there any known downsides to using these new fiberglass springs?

Downsides... How about recycling? Steel just gets put back in the furnace whereas fiberglass goes to the landfill.

Do they burn? These springs will be in close proximity to red hot disc brakes. I've seen fibreglass cars seriously burnt out.

Think so......it has problems when it gets wet fro prolonged period.

There is LOT of problems with fiberglass - I know because I design it for heavy industry. I simply do not believe that at the end the customer will have any benefit from it... Manufacturers are only trying to rip out more and more money from us.

The surest way to save fuel is to go slower, accelerate less and to brake less. When it comes to suspension and spring materials you need to minimise the energy lost in internal damping, so a less comfortable ride. So drive more slowly too?

The debris that damages the paint on the steel springs, what does it do to the fiberglass?
I haven't heard of disproportionate problems with the fiberglass leaf springs.

I doubt that a marque such as Audi is going to put into production a component that does not meet their performance standards, which considering Audi's status, will be quite high. They have a lot riding on ensuring that their models are both safe and reliable.
Whilst a road spring failure is not necessarily too dangerous because the car will be able to proceed by riding on the bump stops, a failure could cause an accident, which in turn could cause fatalities. As for reliability, it will be tested exhaustively, both on a rig and on a pavé circuit with a considerable number of kerb strikes thrown in for good measure. There will also be a lot of whole vehicle testing in all sorts of climates and road conditions.
Considering the reduction in unsprung weight and what that means for ride comfort, I imagine that this is only the first of a range of components to be manufactured using this material.

Nothing new about composite springs, they weigh about 1/3 of a steel spring, last longer and reduce unsprung weight.
Amongst other vehicles, Chevrolet Corvettes have had them for years and my wife's Nissan Serena has one.
However, all the examples I have seen have been leaf springs - a sadly underrated configuration that can save a huge amount of space and height.

Since the Corvette has been using composite springs for 50+ yrs, it's about time, Audi, others catch up.
For springs Composite have a natural dampening and quite steel does at 30% of the weight.
And proves there is no reason not to build an all composite car chassis/body at 50% of the weight with 2x's the strength in cost effective medium tech composites, not CF which is mostly costly hype.
Dziks, I can't believe you are in the industry making statements like that as I've been doing these in high tech racing boats, etc for 45 yrs now, not new at all.
I also have a 2x's stronger than steel at 50% of the weight body/chassis that also proves you are not correct.