The Logitech K700 does indeed work with the Sony NSZ-GT1; I have both.
Agreed, I tried it last night. Nothing extra was necessary, I just plugged in the dongle after the player booted up, and it started working. It was a little weird during setup because it wanted me to "pair" the sony remote by pressing function + Enter, but that didn't seem to do anything when I did it on the K700. But I just pressed a few buttons one at a time (not mashing around) and I think pressing escape moved me forward in the setup process.
One other small issue during setup was when it asked me for my tv model, and when I chose LG, it didn't work. I just skipped the step (even though it told me certain things wouldn't work if I skipped the step), and everything seems to work just fine.
As far as functionality of the unit, I haven't played with it enough to say much. This is my first blu ray player, so we watched the latest Spiderman movie, and watched a few Youtube vids, but that's about it. I did a couple of searches in the app store, and confirmed it is limited.
I purchased the iMito MX1 and will play with that this weekend. If it works well, I'm assuming it will render anything "smart" about the NSZ-GT1 to be useless. I'll have to decide if I want to just keep it as a blu ray player, or sell it and just get a plane jane player.