I have both Hauppauge and Terratec tuners on my rigs. Both are equally good, and are outstanding when used with Windows Media Centre. However, if you don't have Media Centre, the Hauppauge WinTV software is truly dire

With Media Centre, you can record as many shows as you have supported tuners, or you can watch and record simultaneously. How many tuners are supported is a bit complicated - with Win7, it's easy enough, you can have up to 4 tuners. For Vista, how many tuners were supported depends an what region you are in, it was 2 tuners for Europe, but I think 4 tuners may have been supported for North America. I think only 2 tuners are supported on WinXP MCE, but I may be wrong about that, it's possible that 4 tuners were supported in North America on that too.

You can have tuners in any combination of hardware that you like - 2 twin tuner cards, for example, or 4 single tuner cards, or a twin tuner card, and a couple of USB tuners.