I was getting ready to buy a Roku Ultra (or maybe stick; haven't figured out why one over the other yet), but I saw a LOT of complaints about problems with the Roku Ultra. (I was going to buy it simply because Roku says that's its best unit.) But Amazon is loaded down with similar complaints as well. I've started to feel that buying a newer Roku is a crap shoot: maybe the one you get will work perfectly, maybe it won't.
Some problems seem to be associated with higher levels of image quality on 4K and UHD televisions, and some with a thing called Plex. Others involve clicking audible sounds coming from the speakers. I myself have had problems listening over the remote's headset port on a more recent iteration of the Roku. Fortunately, I don't often need to listen through the remote, so I can live with that particular issue. Still, re-pairing the remote with the base unit is a pain because I always have to re-research how to do it.
On the whole, though, are the Roku Ultra and Stick pretty reliable products? I don't want to buy something that's going to be a headache. I can probably find an older model on Craigslist if that's what I need to do.
If you're a basic user that isn't asking a lot out of a $50 device, the stick will work just fine for you. You *might* want to buy a short HDMI extension cable at the same time so that you can move the stick around the back of your TV to help with any possible interference. Roku does provide these free, but they are out of stock.
I have an Ultra on a 4K TV, and run the audio through a Yamaha AVR. The only major issue I ever had was with my original HDMI cables, which weren't adequate for 4K 60 Hz framerate. Once I replaced my cables I've only occasionally encountered the HDCP error screen. Running through my AVR, I've never encountered any audio noise that wasn't part of the audio track. I'm not trying to minimize the issues that some have had, only pointing out that it doesn't happen to every box under every configuration. From what I've seen, the biggest issues are with Denon AVRs, and sometimes with soundbars. . I have an older Stick (3600) that is also flawless. It doesn't do 4K, but have never had any issues with it.
Dan Roku Stick (3600), Ultra (4640), Ultra (4670), Premiere (3920), Insignia 720p Roku TV, Sharp 4K Roku TV, Nvidia Shield, Windows 10 Pro x64 running Serviio and Plex on a wired Gigabit network.