You may want to consider getting two separate devices, the Elgato Turbo.264
for encoding, and another device for viewing and recording--depending on your other requirements.
You and Spongy haven't mentioned how you plan to receive TV signals. Will you be using analog cable, digital cable (QAM), or digital antenna? If you're using analog cable, then you'd definitely need a firewire interface. The amount of bandwidth it uses is around several hundred Mbps and USB 1.1 won't be able to handle it. In fact, when I have two analog cable devices going into the same USB 2.0 port, which is supposed to allow 480 Mbps, I get an insufficient bandwidth error and no signal on one of the devices. So consider getting the EyeTV 200.
If you're using digital cable or digital antenna, then it will use about 20 Mbps of bandwidth for HDTV. Since, I think, USB 1.1 allows a throughput of 12 Mbps, you'd have to reduce the resolution by roughly one half. However, two other options are to get the EyeTV HDHomeRun which delivers the TV stream over ethernet, or, to get the EyeTV 500 which delivers the TV stream through firewire. One thing to note is that the EyeTV 200 and 500 do not need an AC adapter, they can be powered through the firewire port.
Also, if you're dead set on getting a USB device, consider getting the Hauppauge WinTV HVR-950. It's the exact same unit as the EyeTV Hybrid except that it comes with a portable antenna, while the Hybrid comes with component breakout cable instead of the antenna. You can find these new on the Internet for around $65, and you can find them used on eBay or Craig's List for around $50. You can then buy the EyeTV software directly from Elgato for $80.
One more thing while I'm at it. If you want to record a show while also watching or surfing in another window, then you'll need two streams coming into your computer. Therefore, you'd need to buy two devices. (The HDHomeRun is an exception because it has two independent inputs on the unit.) Beware of the EyeTV 500, it also appears to have two inputs. However, one of them is for digital antenna while the other is for digital cable, and only one of them can be used at a time.