Experience with FlixBus

Rome2rio only lists available options, it is not a recommendation.
Flixbus is usually fine, but a bit less reliable than trains. Bruges to Lille is easy by train (change in Kortrijk, takes about 1h30 total) so that's what I would do.
I'll add that Belgian train fares are pretty cheap, so tickets should be less than €20.

This said there seem to be works on the tracks at the moment so if your trip is soon, then maybe the bus is best.

I've not used them but I know people in Germany who have. They are generally slower than the regular trains, but also much cheaper. I would go to their website and plug in your data to see how much you can save. After that, do a calculation with the regular train service, then decide if it's worth it. https://www.flixbus.com/

I have nearly been run off the road twice in separate incidents by their drivers, one was on his mobile phone texting! I wouldn’t use them even if the travel was free.

I travelled by FLIX bus from Innsbruck, Austria to Garmisch Partenkirchen, Germany about three years ago. Fine, no problems, cheap. Pick up was at a gas station parking lot and drop off was outside the train station.

Thanks everyone

I've used them a few times in Europe and they were fine. They've expanded to operate in the US now - e.g. they have bus service between Portland and Seattle.

We rode like 6 years ago from Vienna to Bratislava for a day trip and it was fine. :)

My nephew in Germany uses them to go everywhere. He is happy about the price!

I went round trip from Frankfurt to Trier on a Flixbus with a frequent poster here that lives in Frankfurt. The bus was faster and less expensive than the train. The bus was comfortable, but the driver was on his phone a lot. My travel partner reported him. He was the driver for the return trip the following day and he wasn’t on his phone at all. He did give us dirty looks. I’m sure he figured out who reported him since we were sitting at the front.