After about 10 days experience and some refining of my setup I can give the Lenovo Q190 an unqualified thumbs up as an HTPC.
It's running Windows 8.1 with a Start8 Windows 7 style Start button/menu. It's a fairly powerful PC so should work well for Windows based Home Automation applications. It has 6 USB ports so can connect to peripherals. There are optional add-on DVD R/W or Blu-ray player drives. The fan is inaudible unless you are within a few inches. I doubt I'll ever need the 500GB HDD but others may find it useful. I believe it's eligible for a free upgrade to Windows 10. I'm not certain that it can be downgraded to Windows 7 but it included MS Office so think that means it's a business PC which does allow for downgrading (with a W7 DVD).
I have Firefox running with tabs for Google News, Amazon, Netflix, Crackle, Google Calendar, this forum and local weather, switching seamlessly between them. The user interfaces for Amazon Prime and Netflix are easier to navigate than the Vizio Apps that came with my Smart TV. I did find I needed to be closer to read prompts, etc. so have rearranged the furniture accordingly.
I'm using an MS wireless USB KB/Touchpad. I have disabled the swipes, etc. so the touchpad now only supports moving the mouse cursor and right/left mouse buttons. I'm not sure it works the same way for other interfaces but, for Amazon, the KB spacebar pauses the video and the L/R arrow keys are equivalent to FF & RW. I would like a larger mouse cursor but that's not an option with my setup.
It connects to my network via WiFi and can see a 1TB HDD attached to my router via USB.
It would be very handy if the KB incorporated a learning IR remote in order to eliminate the TV remote.
I did not need this as I have Amazon, Netflix & Crackle Vizio Apps but, with new streaming sources popping up daily, it should provide some future proofing. And, it has made the laptop I kept beside my recliner superfluous.