If you have an open PCIe slot in your PC then using an internal tuner is better than a USB.
And if you do not have a PVR then for about $130 you can get a dual turner with remote (WinTV-HVR-2250 MC) and your PC becomes your PVR capable of recording two shows at the same time while you are watching another show live on the HDTV.
You can then toggle from from your HDTV to the PC to view the guide or play recorded TV or other audio/video media on the PC.
But chances are you'll be watching on the PC because you'd select the show from the guide with one click and only watch on the HDTV when both tuners in the PC are busy recording.
As an hour of recorded HDTV can create a 4 to 7GB file you may consider a second large hard drive (1.5-2TB~$120) if you entend on keeping a recording library.
Of course you will also be able to watch live and recorded shows on other PCs on your network (including Wifi if you have an N router) and NextPVR will go beyond that and give you access to your liveTV and recordings from any PC anywhere with web access or your smartphone.