For reasons now unclear, I decided to make my first edit to Wikisource in early July, 2023. Clearly, I didn't find it appealing at the time, as I made two smallish edits and returned to Wikipedia. However, this January I skulked back with a project in mind: add more poems by the romantic-era American poet William Cullen Bryant. I uploaded a scanned version of one of his books from the Internet Archive (therby creating an "Index" page" at Wikisource), and proofread the pages of a random poem. Poetical works of William Cullen Bryant proved a difficult first project: it was a collection of poems, which inevitably needed complex formatting, but it also had images which had to be extracted (in my case, poorly so) from the scan. After proofreading the pages of my poem, I boldly created a mainspace page to house the poem, with the text being transcluded from the proofread pages to the mainspace to form one cohesive, digitized whole. After eventually figuring out "section transclusion", I happily added the poem to the list of New Texts, not realizing that I had mis-transcluded the poem and an entire page was missing! Although the technical help pages were confusing at times, I found experienced Wikisource users very helpful and patient. When asked for comment, WeatherWriter (talk · contribs) agreed that getting started was difficult:

Getting started on Wikisource was so much different than getting started on any other Wikimedia project. Actually, I struggled to even really learn how to get started. Unlike Wikipedia, there was no “learn to edit” style of buttons to click. They just have a “Help” button, which then takes you to a very short beginners guide. In terms of getting started, it probably has one of the worst layouts for new editors of any project. After that, I discovered you actually need gadgets on, especially for new editors. Every pages has a “header” for basic information. However, only going into your preferences and turning on specific gadgets allow it to be automatically generated. So my first ever page was actually a weird copy/paste from an existing page, rather than a guided creation.

[...]

To conclude, Wikisource is a major perk for weather-related articles on Wikipedia and I would love for every editor on weather-related articles to use it, but honestly, the guide to newcomers needs a major revamp (maybe similar to have Wikimedia Commons’ newcomer process works) before I would personally send a new editor there.

However, it should be noted that WeatherWriter was including free content from webpages, while I was using scanned books, so we were entirely different editing spheres.
I continued proofreading pages of Poetical works of William Cullen Bryant through January, while dabbling in a few other projects, and participating a little in February's "Proofread of the Month".
I found my current project in mid-February: another (shorter) collection of poems by the Australian poet Adam Lindsay Gordon. But contributing to Wikisource is very time-consuming. Here's what Duckmather (talk · contribs) has to say about that:

Each wiki is a huge time commitment. When I joined Wikidata last year, I got concerned about whether I could still keep up editing on Wikipedia; but now that I'm active on three wikis (Wikipedia, Wikidata, and Wikisource), my activity here on Wikipedia has dwindled a lot. [...]

Wikisource in particular takes lots and lots of time. Even a single page can easily take 15 minutes to even an hour to proofread or validate (depending on how much text there is in it; and at least when I do it the way I usually do, which is retyping out the entire text from scratch and then diffing against either the OCR'd text or the previous version). Short 5-10 page pamphlets can take days or weeks, and entire books are unthinkable. Further, editing Wikisource requires a monomaniacal focus, unrivalled by either Wikipedia or Wikidata (except, perhaps, hardcore sourced content work here, which I admittedly do very rarely).

I don't proofread the way Duckmather does, (I'm lazy and I just read the OCR'd text and compare it to the scan as I go), but it still takes a lot of time, especially when the text is small. However, sometimes the automatic transcription is so scrambled as to be useless, so I use Duckmather's more rigourous approach—which in the case of this 1910 newspaper, will take a very long time.

I also started "Florula Mortolensis", a list and description of plants found at La Mortola around 1905. It contains some handy information that I suspect can by used to expand a few of our own articles, besides interesting formatting.

This leads me to the use of Wikisource. Here's what WeatherWriter had to say:

Besides getting started, the process is fairly simple and it actually easier than creating English Wikipedia articles. As an editor who contributes almost entirely into weather-related articles, it is a huge perk to be able to have Wikisource articles. For any U.S.-weather event, the primary source is always the United States government, specifically the National Oceanic and Atmospheric Administration. Since everything U.S. government publishes is in the public domain, it can also be added to Wikisource. So now, weather-related articles can have links for readers to a Wikisource-version of the primary U.S. government sources for tornadoes, hurricanes, winter storms, floods, etc...

Duckmather says, on a slightly different topic:

Wikisource is also (like Wikidata, and the rest of the smaller Wikimedia wikis) hugely under-marketed. The impact of Wikipedia on daily life and pop culture can't be understated; however, the impact of Wikidata and Wikisource, however, is pretty much zero. I've heard of proposals to rename the "Wikimedia Foundation" to the "Wikipedia Foundation", and even though I don't agree with it, I can very much understand why they'd do so.

Wikisource is a library of free texts, including encyclopedias, plays, poems, laws, and novels. There's a considerable amount of work to do, and vandalism is rare. I've enjoyed contributing to Wikisource, as much or maybe more than I enjoy editing Wikipedia—and I plan to continue contributing for the foreseeable future.

• Wikisource for Wikipedians
• Help pages
• Introduction to Wikisource
• What is Wikisource?

• Help forum

• Help with proofreading