I just went through this myself. Got a new entertainment center and wanted to upgrade the TV.
A smart TV was top on my list, so my wife could use it for looking at the kids' Facebook and photo uploads, and my daughter could use it for videos and games.
I almost bought a Samsung smart TV because (1) it could do things with my smartphone, (2) it was a deal on Amazon, and (3) I liked the idea of perhaps writing an app for it myself.
However, after reading reviews, it became apparent that the LG smart TV was viewed as easier to use. Unfortunately, it was missing some apps that I wanted for my wife to use.
In the end, I decided to keep the smart part and the TV separate, so that I could easily upgrade either piece. So I started with a Roku box for the smart part (it has Netflix, Amazon Instant, Facebook and Flickr and a great search facility)... and an inexpensive refurb'd Westinghouse for the TV part. Lot cheaper, too.
I wish I knew more about XBMC.