I used SageTV for a while before Google purchased it and ended new development. Now that it's being open sourced, it's becoming interesting again. Unfortunately, SageTV is built using Java. And Java has been a thorn in the side of many users - just look at their support forum threads!
As to where-to next, I'm taking a wait-and-see approach. But I did back the HDHomeRun kickstarter
. And I have high hopes.
The big plus about Windows Media Center is that it has a really smooth user experience, it was free, had solid tuner support, and a free guide. The big downside is that Microsoft never released a software-based extender, and they stopped new development post-Windows 7.
The HDHomeRun software will be subscription-based ($30/year), but it comes with guide data, which costs ~$25/year from Schedules Direct. They have committed themselves to creating many different client apps, which is a big win over what Microsoft did with Media Center (and, frankly a big win over SageTV).
Really, the one and only issue I take with the HDHomeRun project is that while they're making a Windows client application, they've never stated that their app is going to be a Universal App. At this point, I think it would be insane not to make it a Universal App, but it concerns me that I haven't seen it stated anywhere that it will be a Universal App. And they talked about the possibility of creating a separate Xbox One app, which suggests that the Windows App that they're making isn't Universal. If the Windows App was Universal, I don't think they would be talking about it and the Xbox One app as two separate things.