I have been using Fiasp with my pump for a couple of years.
I have had no issues but there are some people who find Fiasp does not suit them.
I have noticed a couple of things
- the out of the fridge shelf life for Fiasp is not as long as other fast acting insulins such as NovoRapid
- the speed at which Fiasp works seems to depend on my starting blood sugars. If I am in the 4s or 5s, Fiasp starts pretty much straight away. However, if my levels are over 10, it can take nearly an hour to work.