If you are into emoticons, you can use custom emoticons of one server on another. If you share files, such as clips, until recently discord allowed only 8mb on free tier. Now it is 25mb, but can get up to 500mb with nitro. Video streaming is limited to 1080p at 30fps, nitro unlocks up to 4k with 60fps.
Basically allows more bandwidth and storage on their servers, which is understandable I think.
So far as I know, they’re not shoving 20 ads in your face on every screen.
I know they’re far from perfect. Heck they have a forced arbitration clause in their ToS.
But compared to other services lately, Discord seems to mostly be trying to treat users as customers instead of products for advertisers. I’ll take it, and get some neat conveniences from Discord in turn.
I have the basic $3 one, I just call it my shitposting tax. Longer messages, using emotes in any server and larger files. I use it a lot since my friends haven't warmed up to Matrix yet, might as well support them while its not total trash
I mostly just pay for it because I've used it for ages and definitely get more value out of it than the subscription cost. I don't think I use a single nitro feature.
They send random gifts some times, usually a code to redeem something in a game I don't play.
Some super reacts - animated emojis basically.
Other than that I really couldn't tell you. I don't think the subscription is worth what the subscription gives, but the alternative is the free product gets worse faster, and that would disrupt a lot of communities that I enjoy interacting with.
Thinking of Discord as a whole, I think it is worth the nitro price. Not in love with the trajectory though.