is it worth it?

In my experience - not really.
The app hasn't really been maintained or improved from 2017-2018. Which causes some issues.
First of all you are severely limited in which wireless controllers will work for you. There are basically 2-3 wireless controllers that still work, and can still be bought. All the other ones are incompatible. And the ones compatible - are not manufactured anymore.
Secondly, the streaming quality is limited (you can't stream HDR, you can't stream more than 2 audio channels, etc.)
And in case it doesn't work well - there's nothing much you can do.
I recommend to the Nvidia Shiled, or any other strong streamer or mini PC instead.
SteamLink app currently has Windows, Linux, iOS and Android versions. So basically anything you can connect to your TV can be used to stream games to it.

Any reasons I should avoid it like the plague?

See above.

How exactly does it want you to connect your computer, and what if it's in another room?

Preferably with the ethernet infrastructure running through the walls of your home.
If not, then an ethernet cable.
If not, then internet over cable TV or power outlets.
And worst possible solution would be wifi - which will probably introduce significant lag.

Won't connecting over wifi cause lag/latency issues?

Yes, it will.
It is not recommended, no matter which app you use for streaming.

Any more issues if the computer is a Mac?

No.
Your limit will be the games the Mac is able to run.
And take into account that any streaming adds 10%-20% more load for the streaming itself - so I wouldn't stream from a laptop for example.
(Gaming PC is the best place to stream from)

Originally posted by Mdk25:

is it worth it?

In my experience - not really.

thank you very much @mdk25, this is so helpful, I really appreciate it.

Originally posted by Xenophobe:

Your best bet would be to get a raspberry pi 3B+ or newer and use the link app for it, no region locking outside of the usual game specific censorship.

Surely that would mean playing on a little laptop though? Or am I missing something here?

Originally posted by Xenophobe:

no, the pi acts like a hardware steam link. .

Oh right, so like a dedicated mini computer? Have you tried that, is it a good way of doing things? At the moment I'm connecting a laptop to a large monitor and using wireless controllers. It's not very efficient but it does work. Was trying to streamline things a bit more.

Originally posted by Xenophobe:

I used a pi 3B+ .

Definitely an option to consider then - do you not have that setup now?

Originally posted by Xenophobe:

I still have the pi, /quote]

You've blinded me a bit with your tech abilities there I'm afraid, I stopped understanding properly after the first sentence, and I can't even make your quote separate from my reply :P but in general it seems like the Pi might be a fun idea if I get fed up with the current ridiculous setup I currently have, so thank you.

Originally posted by Xenophobe:

apologies ... pi-hole explained better than I could: https://en.wikipedia.org/wiki/Pi-hole

Thank you :)