Particularly appealing are the two service providers, TiVo and Replay TV, that go hand in hand with a PVR, allowing you to record anything at any time. You will have to choose between these two when choosing a PVR. These PVRs are comprised of two parts...the actual PVR hardware and then the subscriber service for scheduling data. TiVo has their own PVRs but have also licensed their software to manufacturers Pioneer and Toshiba who have built TiVo into their PVRs. ReplayTV have their own PVRs under the DNNA make. The ReplayTV tends to send a superior picture while TiVo excels in programming. Both platforms allow you to record programs based on star, type of show, or even a keyword. If you want to see any program with Bob Denver just enter it and any show with his Gilligan-ness will be "taped". Another option allows you to pause a program you are watching to talk on the phone, run out, smell the roses, pop back in and resume the program. Nice. Along with some standalone PVR models come home media options that can connect with your pc. Capabilities allow you to remote program from a web browser or record streaming digital music as well as transferring programs from your PVR to your PC's DVD recorder.
Unfortunately the more appealing the options, the higher the price. A low end TiVo might cost around $50 but add on service costs of $15 per month or $300 for a unit's lifetime plus more for added features and you are at a considerably higher price point. You are also looking at another box with wires in your media area and considering the analog to digital conversions at the source, a lower quality picture.
Note that if you are watching TV via a cable or a satellite service, you might be able to swing a PVR for relatively little financial outlay. Cable and satellite companies are combining PVRs and their own software with their boxes for $50 to $300 (you can upgrade your current box) and if you are a new customer, you might get a better offer (along with a service contract). Look for dual tuner boxes that allow you to watch one program while recording another. Although they are not up to the standalones for features and ease of use (some complain of lower end PVRs reliability with the units erasing shows, missing others, etc.), the price is right. Then add a stripped down DVD recorder for other DVD requirements.