It was a bitch to get it to work right and when I was young I didn't have enough storage to really use it properly but "MythTV". A open source Linux based DVR system that basically told the companies to fuck themselves. It had built in commercial detection (that mostly worked) back in the early 2000's.
Yeah I took a look at MythTV a couple of times over the years but I was never really into 'all in one' solutions and it seemed too much work for an add on.
Like you say all you really need is a pc and wireless keyboard and it's never been easier.