I am using Fire Stick for past 1.5 years or so. I bought the 1st gen back in 2016 beginning. I am in US so my primary source of entertainment is streaming only. I have Kodi side loaded on this since day 1 (now updated to Krypton 17.1) and use various addons to watch LiveTV. I do not use Prime videos as I don't have anything to see there and I won't be even renewing my prime once it expires. I use Youtube and Netflix and they work pretty well. For a primary entertainment device, I should have bought a FireTV Box instead but since it was my first foray into Kodi, I wanted to invest less. But the stick is still serving me well and works as expected. No issues whatsoever. I like the fact that I don't have to point the remote to the TV.
The only minor issue I have found sometimes happening is that my videos on Kodi and other *cough*live tv*cough* apps (but not netflix, youtube) would stutter and frame rates would drop with lost audio. I always though that it was probably due to unreliable streams from not so dedicated servers. But in an attempt to fix it, I tried this, I put the firestick in fridge for 20 minutes as it was warm (not hot) to hold. After reconnecting, this were back to normal. I do this only when restarting the stick does not help. I use my TVs USB port to supply power, rarely it will say that power is not enough but it would still work. In my case, I have not really faced wifi issues as my wifi router is just behind the TV so distance between stick and router is very very less.
I many a times think to change and get a FireTV Box but then again, I don't see a real need of that as the stick does whatever I want for now. I never use local playback so having MicroSD slot or USB slot was not a requirement.