Is there any point in signing up for ORCID? I see the point of it it being an independent way to document all your publications, jobs and grants etc. But is it worth a PhD student signing up for it or are there any disadvantages to having one?

It's very useful if you have a commonly used name as it means your publications can be quickly identified. My university wants all academic staff to use it.

Thankyou! It sounds slightly irrelevant but was wondering if there are any long term downsides (like your old Facebook account). But it doesn't seem to matter that much.

You have to be honest on publications anyway so no real downsides. Once you set it up, it updates itself (assuming you're publishing in indexed journals).