Hi SeanC,
I have a P4 with a GeForce3 Agp card running Win2k, and after a bit or research I decided to buy the Hauppauge WinTV dbx with fm radio tuner (model 401). Other vendors also offer a tv tuner only pci card (eg. ATI TvWonder), but my choice was mostly driven by the quality of the driver on Win2k. I'd stay away from an usb external tuner, unless you have special reason to get one (i.e. laptop), since they all use USB 1 at the moment, and compress the video signal to fit into the USB bandwidth with some effect on quality. Aside from USB, most of hte consumer level PCI tv tuner card have similar quality, since they are all based on similar Brooktree (now Conextant) chipset.
At the moment I have to say that I'm not using MJ as my tv viewing application (I use Dscaler), but if easy timed capture and personal-video-recorder functionality become part of the package, I'll probably reconsider since in that case organization will become more important.
Aside from the tv tuner the WinTv has an s-video video input for video capturing: it does not support HW compression, but on my P4 this is not an issue. The sound is handled by connecting the out of the WinTv card to the mic in on your sound card
Ohh, the WinTv comes also with an infrared remote (altough I'm not using it since I have another RF-remote that can be use from anywhere in the house and is easier to customize)
Scronch: sorry I do not have much experience with USB external tuner for laptop... someone else will have to fill in. My guess is that in the next little while, as USB 2.0 becomes widely available, an external solution will be completely on par with an internal PCI, but at the moment they arent and I haven't seen any USB2.0 tuner yet
Claudio