I personally bought a 2011 Samsung (55" D7000) and love it, but I bought it right after CES when the 2012 sets were announced. Therefore, I got it for a super outrageously cheap price (I think I paid just over $1000 for a $2500 TV). In response to a couple fo your questions, yes the Samsung TV connects to 5Ghz networks, but make sure your router is close by and not blocked by more than 1 wall or your network speed will suffer rather horribly.
For 3D, I have it and can say I have used it maybe twice for movies. It is neat but not particularly useful. The nice thing is that the processor required for 3D makes everything else for your TV better though. As an example, imagine if you have a choice of two computers. One is made for internet usage, the other is made for extreme gaming. Obviously, the extreme gaming PC doesn't ONLY do gaming well, it is exceptionally fast and does everything far better than the internet PC will. Also, If you have a PS3 then the 3D gaming ability of the PS3 is awesome, and I use it all the time. =D
If you find a good price for a Samsung TV, you will certainly not be disappointed. With that said, I'm sure you would be just as happy if you bought an LG, Sharp, or Sony as well. When I worked for an electronics retailer it was the rule of the 3 S's: Sharp, Samsung, Sony. LG has certainly made its case in recent years however and are starting to make great quality panels.
The only downside (in my opinion) to LG is that their 3D technology is subpar. They use passive glasses which normally would be fine, but any time you watch 3D content your resolution will be downscaled to 720p. The benefit is lack of "flickering" from the shutter glasses, but with new TVs that run at 240hz the flickering happens 120 times per second per eye, which is way beyond anything your brain can perceive. If, however, you decide to buy a 120hz 3DTV you may notice a slight flickering from the glasses as it will reduce the shutter speeds to 60 times per second per eye.
Also, you can indeed rip a 3D blu ray and play it over your network, there are many guides online for you to follow to help you out with that. There are also many things in 3D now, not just animated movies. The Avengers and Avatar are just a couple examples, but there are now tons of 3D movies being released to help push Blu Ray sales and drive sales overall. It is still a rather gimmicky feature though overall (in my opinion).
Good luck with your purchase!