I'm frugal. People who know me personally might say cheap, but I'm writing this so I'll say frugal. I've never bought a new computer in my life (and in fact could argue that I still haven't) and I definitely tend toward either building my own or buying lightly used, since most people really don't need the cutting edge of technology (or the bills that come with it.)
I built a Hackintosh from a Dell Mini9 refurb early this year, and have really enjoyed OSX in spite of the tiny poorly-laid-out keyboard. I have for some time used a Dell Latitude D610 that I bought used as my "TV computer" for watching Hulu or Netflix on the flat panel in our living room, but the improving image quality of streaming sources and displaying them on a 1080p set was starting to point out the Latitude's shortcomings.
One of the important considerations of a Home-Theater PC is noise. One needs a quiet machine to avoid having fan noise interfere with quiet passages of movies and music. One of the quietest machines on the market is Apple's Mac Mini, and they've recently upgraded it significantly with nVidia video processing and a 1066-MHz front-side bus, so I decided to give it a shot for home-theater duty. True to my frugal nature, I scanned the list of Apple refurbs for a few days until I found a base config (1g RAM, 120g hard drive, 2 GHz Core2 Duo) refurb.
I've had the machine 5 days now, and so far I'm quite pleased with its performance for my needs. I'll point out here that I wasn't going for a full PVR system, I have a DVR from my cable company and I'm happy enough to use that, or I'd have needed a dedicated system like the Tivo HD or a Windows-based system so I could use cablecards. I'm primarily using this for Hulu and Netflix and music (streaming and shared from my primary desktop in the house.)
The configuration was Apple-easy, though it's a bit snotty about recognizing my wireless keyboard on a reboot. (It's a 2.5 GHz keyboard with a USB dongle, not bluetooth... I have to unplug it and plug it back in after a reboot and then everything's fine until the next reboot.) Silent, stable, plenty of open-source choices for my needs. I'm using Plex instead of Frontrow, since Plex gives me nice integration with Netflix and Hulu and other sources. Video performance is good, though I'm still trying to tweak the desktop UI to be clear enough from across the room (the Plex interface is fine.) It's an almost-new machine and I'm quite happy with it... if I keep drinking all this Apple kool-aid I'll end up with a Macbook Pro.
So now for my personal machines, I'm at 2 Windows (XP), 1 Linux (CentOS) and 2 OSX... just in case any readers wonder if I really AM a geek!