I have a Freecom USB DVB-T and it can fussy at times, bundled software are rubbish, there are plenty of third party software out there, some good some not, so far on my usb, progdvb, mdeiportal and powercinema have worked, out of those three powercinema is the best as the usb stick seems to work very well on it, other are fussy and it doesnt even work on WMC.
Signal strenth is good on mine, i'm using the supplied ariel which is made form metal and i need to put it on my metal bed, which makes the signal strong
, i find the freecom good for casual use, but if your gonna watch tv reguarly on ur pc, go for a pci card, i'm thinking of buying one myself, cos the freecom can be frustrating at times, not sure if the recent usb tv sticks are improved tho.
One thing to lookout for is the chipsets and so on used, going for a popular model means more support is abiable for it.