They're about as good as you could expect from a major cloud storage provider. In theory the encryption means that Mega can't access your files, but they're expressly very cooperative with government agencies so don't bet on anything you put there being entirely secure. I haven't heard of any major problems with them though - it's what I've been using for cloud storage the past few years and I haven't had an issue. As long as files aren't shared and therefor at risk of being reported there's not much to worry about, though in the case of things getting reported it's a 'take down first, ask questions later' type deal.

Here's a transparency report from them (how much to trust it is up to you): https://blog.mega.io/mega-transparency-report-2021/

I didn't even know that mega was still around, I thought they got shut down after a police raid.

Ive been using mega for over 6 years already, haven't noticed a problem at all. If u are fed up of their downloads/uploads limit, theres an opensource project on github called (Megabasterd) , it allows u to download any amount of size of contents hosted on mega cloud for free without paying up for their subscription. U can additionally use proxies(proxyscape) to speed up ur download speeds upto 100s of mb/s.

I have been using it for the past few years. I haven't had any issues so far.

It's a hosting site. It's as trustworthy as the person who uploads the files.

I don't know what you have in mind with "trustworthy", and about what, so maybe this comment is worthless for you. But I've been using their cloud storage for several years (like other commenters here), for work-related files, and to sync them between computers and phone. Their syncing system and apps are actually great. No complaints on my part.

My friend and I jokingly call it MegaConz after its FQDN, that’s about as much as I trust it