TVTime is a nice application for those of us who own a TV card, and it is known to offer the best quality from all the applications with the same goal.
Of course, it doesn't compete with the programs manufacturers provide, but given that they are only available on Windows, TVTime will be a good solution for watching TV on Linux. It offers basic features, like settings for contrast and brightness, together with easy to use shortcuts for taking screenshots or the fullscreen mode.
Actually, the simplistic approach is what impresses me, but I really miss a recording feature. It works very well with my Leadtek TV2000 XP Deluxe card, and you can find a complete list of supported cards on the official website, here.
You can also find a FAQ and a complete list of shortcuts available to TVTime.