We've got a 40" Samsung Smart telly from about 4 years ago (not 3D, not wireless)
The 'SMART' is pretty good we've but since got Virgin Media Tivo to do most of the same tasks.
Connecting to my network drive for family photos and videos is great. You can similarly connect to shared drive on a PC/laptop. I use Powerline adaptors which I find more reliable than WiFi.
Youtube is a pain to use, same on Tivo, just not as easy as a laptop/PC. However I can browse on an Android device and then divert it to the telly. I was gob-smacked the first time I was playing music on my tablet and it asked 'Do you want this to play on device TV?'
iPlayer works OK
Don't use any other pay on-demand services
Speakers are weak on mine, got a cheap soundbar sat in front
The only problem we have is the screen image being corrupted when we first turn it on. We have to leave it for a couple of minutes and then switch off-back on. I've been told this is common to lots of different brands as they all use the same cheap Chinese cables. I suspect the connectors are tarnished as when I took the back off and unplugged/replugged every connector, it was OK for 3 weeks.