I'm currently using a MyHD card primarily for playback; it's still the best way for me to play MPEG2 on an older computer without taxing its CPU or video system. I added an HDHR, using CW_EPG to schedule recordings on both devices. CW_EPG doesn't have a nice grid like TitanTV so it isn't as easy to schedule one-off recordings (although you can) but it is much better at recording recurring shows. It uses info from a Schedules Direct subscription ($20/yr) and also populates MyHD's OSD guide with that info, replacing the normal PSIP guide. If I needed more tuners I'd definitely add another HDHR. BTW, CW_EPG also works with Fusion tuners.
HDHR advantages: Due to its Ethernet connection and minimalist interface, it works or can be made to work with just about anything: Windows, Linux or Mac running several different multimedia programs. It's one of the few tuners that enables clear QAM tuning under Windows Media Center. New motherboard designs won't make it obsolete.
HDHR disadvantages: Most people will want to use software other than what it comes with. I tried TotalMedia, didn't like it and deleted it. But there are many other choices, some free, some not. Also, since it uses UDP data transfer, the receiving computer must
be ready to deal with the bytes as they arrive or they'll be lost. I had lots of glitches in my files until I switched from an Ethernet port with an unadjustable and probably small buffer to one I could enlarge. I still have occasional glitches when the computer is busy doing something else such as opening the MyHD app (once opened it's OK).
It's getting increasingly difficult to make a MyHD card work with newer hardware and Windows versions so I can understand why many are abandoning it. An ideal solution might be a networked media player (not sure which one) fed from a separate file server that runs CW_EPG to collect programs from a bank of HDHRs.
I haven't tried MythTV on Linux yet, but from what I've read that might be another good choice. It too supports the HDHR.