I use the Rii and the K400 regularly and love them both. The Rii I use on an NVidia Shield Pro in the bedroom, while the K400 is on the HTPC in the living room. To me they are perfect for what they are doing, the Rii small form factor for watching videos or whatnot in bedroom, and the K400 for the HTPC with some surfing and light gaming.
K400 and a dedicated mouse is what I use. Makes gaming enjoyable on the couch for stuff a controller isinot sutup for. The dinovo mini is cool and small but can get anoying to type on there atr also 2 versions one is BT and one has the unifying remote.