I had a $50 gift card to bestBuy so it cost me like $60 out of pocket.

It's small.

The interface is okay - but Amazon keeps mixing things that cost money in with free things. There is a Prime only section but the interface doesn't give enough of a clue where you're at. Luckily you can protect yourself from buying something accidentally by requiring a PIN number.

I installed Kodi on it. Couldn't figure out how to get my Mac OR PC to allow SMB sharing with it (works fine on my PC Kodi) so I ended up installing SMB UP on my Mac. Once I did that then connecting to the shares work fine.

Most things played fine - the forward/rewind functions sometimes locked Kodi for a few minutes. I'd say if you start a movie and watch it you're fine. Pausing it and resume is fine too. But it may lock up if you forward/skip back for some files.

Also Kodi for Android doesn't seem to plat .WTV files for some reason. (From Windows media Center.)

I couldn't get VLC for Android to see any of my SMB shares.

I don't have a 4K TV but I have a 4K Dell Monitor. All the made for Amazon series available for UHD played fine at 4K 30z. They had "Funny Girl" the 1960's Barbara Streisand film in there too and no video appeared when I attempted to play it. I think they may have a few other 4K videos in Prime - but not much.

Issue: Sometimes I'd press a button on the remote and the Fire TV would do nothing - even the light that comes on the front when it senses a signal didn't happen - I see other people on the net saying they had the same problem too.

Issue: No "easy" way to have side loaded apps appear in the Interface. You have to go to Settings > Applications > All Installed Applications to launch it. (There are programs that can map buttons on the remote to run programs - but I'd be nicer if you could see them in the interface.)

I'll keep playing with it this weekend, but it looks like this thing is not a replacement for a HTPC - but could be a nice streaming box with the bonus of Kodi and VLC - but I think it has room for improvement.