I'm kind of a sucker for gaming controllers / peripherals / remote controls etc so tempted to pick one up regardless.
I built a far too over powered HTPC with the end goal of being a Steam Machine (although not as far as to install SteamOS, rather have full Windows for now and stream from within) so the steam link wont be needed.
The reality is that in over a year I've still not played a game through the HTPC, as people in the house are watching the telly when I might play a game! So I just use my desktop.
Maybe with a £40 purchase, the intrigue alone will get me gaming through the HTPC on a Saturday morning wthen the TV is free (something like the Witcher 3)
I have a 65" Plasma and surround sound in the living room, so at least the living room experience should offer something different to the desktop one.
It might well be the case that some games will suit the controller well, others will suit xbox/ps/pc controllers, and others should only be played with keyboard and mouse.
Games like Cities Skylines would look great on a big telly but I can't imagine using anything other than a mouse! Maybe us old dogs just need to try and learn new tricks!
In summary, surely the controller is worth a punt, especially for those who are already have streaming capabilities but aren't making the most of it.