For OTA HD broadcasts, I could NOT get MCE to work on Windows 7 Professional MCE with my single tuner card, so I bought a dual tuner card, thinking it would work better with MCE. No dice. Still had several channels that had very low signal strength and would not record, even though they would sometimes come in with a live broadcase. Even with a big roof antenna it wouldn't work. I found no help on the internet and even tried moving my TV card outside the computer with a custom PCI extension cable and wrapped in the static resistant bag and tin foil to rule out any within-computer electromagnetic interference someone mentioned.
I finally got fed up and called Hauppauge support and they suggested WinTV7 - it was only $10, so I bought it. Very much worth the price. Now, even with a very small antenna, I get amazing reception (26 miles from the transmitters).
I recall that even a few years ago MCE had trouble with my original single tuner card.
As I said, this was all for OTA digital TV broadcasts, MCE may work if you are using it for digital cable.
So, I use WinTV7 and TitanTV for listings and to set up recordings. Works great. Plex is also awesome for streaming through Roku and to phone. It even plays back the show before it's done recording since the recording format is set up to stream.