Have you used FlixBus? What was your experience?

Flixbus is fine, I think if you search in the forum you will see many other comments echoing
this. It's reasonably comfortable, the bus stops periodically for rest and refreshment breaks.
If the wi-fi works, it's a nice trip.

I'm not sure I'd do a bus trip for 12 hours, but for 3 or 4, it's pretty easy.

I agree, it's fine.
I think I've only used FlixBus once, in Portugal, but wouldn't hesitate to use them again.

I took the bus from Chamonix to Milan on Flixbus in 2021. It was scenic. I remember wanting to get off to check out Aosta. Once you get off at Milan Buss station the metro stop is there to get to Milan Centrale to catch the train to Varenna. The metro is now tap and pay. I was in Milan about a week ago.

I used FlixBus in Germany, and the experience was fine. They were on time. I didn't have any problems, and I wouldn't hesitate to use them again.

We used Flixbus in Croatia. Inexpensive, comfy. I'd ride it again.

I use Flix more than I use trains. Great buses, safe drivers, economical.

I've used Flix in both Portugal and Italy. No issues,

Edit: With so many good experiences, I’ll give FlixBus another try.

Our two round trip FlixBus experiences were not as rosey, Nice- Montpellier and NY-DC. Broken toilets or disgusting toilets, contracted buses on the Barcelona-Milan run with drivers who spoke only Romanian, not Spanish, French, Italian, or English. Not allowed to leave the buses in France during stops despite the broken toilet. Very crowded seats.
DC-NY left very late. Had one break in New Jersey. Very crowded.
Unless there’s a huge difference in time or price, we prefer the train. If one toilet is broken, there are many more available.

I used Flixbus from Macon to Atlanta, Georgia. It was swift and easy to use. I imagine you'll have a more gentille group of passengers.

I used FlixBus at the end of the RS My Way Alps tour in 2022 and it was super easy. On time, clean, friendly driver....I went from Chamonix to the Geneva airport. Have a wonderful time, that tour is amazing!!

Nice enough from Brussels Charleroi airport to Bruges. More like a coach than a city bus. A few years back they acquired Greyhound in North America. I only used them in Belgium that one time so far, but hopefully their buses in USA are now more like FlixBus than Greyhound (those were often quite run down).