My experience is almost identical to Thomas’. Yes, at first there was a bit more of a sting as compared to novolog, but I’ve gotten used to this and don’t notice it. I only do notice it when I have a large bolus.
Regarding how quickly it kicks in for me. When I first started using it (I think about a year and a half ago? Maybe a bit longer than that), it kicked in around 5-7 minutes (confirmed via finger checks). I have those experiments written down somewhere… Novolog at that time took about 30-40 minutes to kick in for me. I had been using Novolog for about 16 years. Now, agreeing with @Thomas, I feel like Fiasp takes a bit longer than that initial 5-7 minutes kick in time. For me, it’s more around 7-12 minutes now, confirmed with finger sticks. But like @Eric said there could be other factors at play in this regards.
I have used Fiasp in both a medtronic pump 670g and tandem x2 and have had no issues. I have heard that Fiasp is not as stable within pumping cartridge and tubing as compared to novolog/humalog, but that has not been my experience. The medtronic 670g cartridge holds 300u and I would replace the cartridge probably every 4-6 days for an idea of how long Fiasp was stable in my pumping supplies and my case.
I don’t think that Fiasp is a miracle insulin, but it helps me a lot with timing of boluses matching my meals since my schedule can be pretty hectic and prebolusing can thus be hard to time out.
I did not have to change much about diabetes management in regards to ratios and sensitivities, but the consideration I would suggest you make is the timing of pre-bolusing may change for you when you start using Fiasp. Like I said above, because Fiasp kicked in for me quicker than novolog, I can prebolus closer to a meal than I could with novolog. (Though I do still need to prebolus with Fiasp).