Twitter doesn't work. Their app now shows _maybe_ 5% of tweets that my logged in user does. Safari is slow as crap on the website.
Google voice still rings and shows notifications, but can't function because no updates are available and something in the api is broken.
A non-zero number of sites show no-css warnings or just crash because it's an old JS interpreter. (HN though -- it's still rocking the 2000 era web design)
Apps that access the network are slowly dying. Though kindle and mail still work, and that's about all I use it for now.
This was a $300 device 8 years ago, and probably has my best $/usage of any tech I've ever had. The replacement is an 800eur ipad (edit: mini, with cell), because it's (the mini) now effectively a pro model rather than the cheap one, and I'm not sure I can justify that.