Assuming you're able I would seriously consider trying MythTV before taking the plunge and paying for Sage. Certainly over in the UK it works wonderfully with DVB-T cards for freeview channels especially since they included the EIT parser with gives an over the air 8 day EPG completely free. American users are also watching HD content with very little tweakery. Since the .18 release it's been really simple to install and the bootable distros make it even easier.

As for Sage, three of my friends wanted PVRs, seeing as they weren't proficient linux people I said they should try it. They all eventually went over to MCE instead after being totally underwhelmed.