The PCI DVB cards have plenty of advantages, and some disadvantages.
The advantages are that, for less than $75 and usually around $50, you have an instant DVR. You can record any stream that you tune with the card directly to your hard drive, and subsequently burn it to DVD
PC-based DVB cards can also receive high definition channels, which makes them by far the cheapest HD solution for FTA. As an added bonus, they can even receive 4:2:2-sampled channels, which most set-top boxes can't do.
The main disadvantage is no blind scan. Another disadvantage is that, due to software signal/quality meters not being very responsive, it is very hard to aim a dish using only a PCI DVB card. For these two reasons, it is advisable to have a decent set-top box in addition to the DVB card. You can use the receiver to blind scan and aim your dish, and the DVB card for recording and HD