Great tip! In encourage others to mention keyboards they've tried and whether or not they have worked.
Just purchased a new Samsung EH 5300 Smart TV and wireless keyboard - Logitech K400 touch pad with built in scroll pad. Absolutely no issues, no linking set up required, nothing. Works perfectly right out of the box. They even threw in a set of batteries!! BTW, I bought this TV in Canada but the 1-800- Samsung guys did not have an answer as to compatibility with a USB wireless device. This one is tested and working.
Have fun surfing !