I use it as a client for a company gmail account and as an rss reader. In my opinion, it's fine. Not great, but not bad either.
The biggest pro it has for me is functionality. Mail, calendar, RSS feed reader,.. maybe even more that I do not use myself. And all of that for free.
On the downsides, I'm not a fan of the design, it feels pretty dated to me. Same goes for the UX, just navigating around gives me some 20-years-ago vibes. But that might just be my personal interpretation.
After all, it's still miles better than outlook and their "over 700 third parties" carefully watching over your mails together with you. And since it is free, why not give it a try and see for yourself?
Company gmail, yeah. Like, the company pays for google services and mail is one of them, which I am required to use. For my personal mail, I am a very satisfied tuta customer.