Yes, exact same problem here. My WiFi is extremely slow. Laptops and other devices seem fine. I've reset my router, modem, etc. I even hooked up and configured a different router last night and experienced the same results. Interestingly, this only seems to happen when connecting to a 2.4 ghz network. 5 ghz from the same router was extremely fast. Perhaps I should upgrade to a simultaneous dual band router. Mine is kinda old and will only do one or the other. I need to leave it on 2.4 since Chromecast doesn't support 5ghz.
I'm also having Bluetooth issues the last week or two, but I don't want to hijack your thread. I'll start a new one about that.