1. I'm in a rural area and internet here is 'almost' not existent at home. We do have an account and receive about 2-3 Mbs speed. I offer this as the Fire TV 3 works only by wi-fi and has no ethernet plug-in. Even with my low speed, I could run the Fire TV 3 alright, but of course streaming is strained. We hope to have the internet speed issue resolved in a month or so.
2. No SD port. Had about 4.89 Gigs free of 5.34, or so before putting my apps on. Currently 3.53 still avail.
3. You can use the Android app, "Apps to FireTV" which works just fine. In fact for me the transfers/installs are much quicker than on my Fire TV 2. When using the app for 'installing', the app does say at the end that the transferred file was successfully uploaded to the Fire TV 3, but the install 'failed', even though every app did end up installing just fine, it just took a few seconds longer than the app transfer allowed for with the notice.
4. AppStarter works just fine for me.
5. Cetusplay and MouseToggle 1.06, 1.07, 1.08 (most recent version) do not work for me. Cetusplay loses the mouse cursor near the buttons I need to activate, and with MouseToggle, the mouse size/resolution has changed so the mouse is much smaller and does not activate what it rests over. At this point in time, both useless. I suspect that the background screen resolution of Fire TV 3 has changed and that may be the reason the Mouse Toggle may be smaller and 'off'.
6. Other apps installed, YouTube, Netflix, PIA, etc work just fine. Netflix HDR movies do view in HDR and I get the HDR 'notice' on my LG OLED tv screen.
7. I wish I could find a good internet browser that would work with the Fire TV 3 remote, and a mouse toggle that works with this new Fire TV 3 OS, and web browsers, as well.
8. SET TV works, but as the download speed is slow, I do get lagging. SET TV is about $20 a month subscription for 3 or 4 devices, 300+ channels, movie channels, CNN, HBO, et al. Very worth the monthly fee. Can't wait to have a reasonable internet connection speed soon... so I hope.
The Fire TV 3 is about as quick as the Fire TV 2 in terms of screen and page freshening. I did mention that Apps to Fire TV installs and uploads seem much quicker. The Fire TV 3, as you know, is much smaller and lighter, and hangs off the HDMI port on the TV. Velcro will work for that. Other than the new HDR output option, I can not say I am 'excited' about the Fire TV 3 yet, and whether to keep it or put my Fire TV 2 back up and wait for a Fire TV 3+, which has ethernet and an SD port.
That's about what I've come up with so far.