So angry to discover that Zotero now charges a fee for storage
I'm angered to discover that Zotero now will charge me for using it. I looked at Mendeley and Endnote and chose Zotero because it was FREE. Now,six months into a PhD (and bibliographically invested in Zotero) with hundreds of references saved, I now receive a warning notice to say that I need to upgrade my storage and pay for it. Endnote was clear that it charged upfront - not Zotero. This is simply not on.
Zotero's own cloud storage has been a paid solution since its introduction in 2009 (https://www.zotero.org/blog/synchronize-pdfs-and-collaborate-with-zotero/), with currently a free allotment of 300 MB. If you don't want to pay, you can either make sure you stay under the 300 MB limit, choose a free syncing solution (like WebDAV), or disable file syncing altogether.
Note that this only concerns files in your Zotero library, like PDFs ("file syncing"). Bibliographic items, which take up much less space, can always be freely synced ("data syncing").
Not worth the hassle for me personally, so I pay Zotero. I don't mind sending $5 their way for a tool that I can't live without (and I'm an incurable packrat -- could in principle have gone with the 2GB version, but naah). Mendeley's cheapest option is also more expensive than Zotero's most expensive option short of unlimited. If you just hit 300Mb, you should be OK for a while with the 2GB option, and compared to EndNote, you'd have to be using it over 12 years before breaking even.