They are pretty cool the only downside is that you must put the modem in a window with a clear view and few obstructions otherwise you will have poor bandwidth or be completely unable to get a signal. I could get full signal in a window but if I put the modem on my desk 5 ft from the window the signal would come in and out.
They are also generally slower than standard cable, plenty fast for 95% of stuff but they aren't as fast a cable yet.