I just got my Zaaptv HD509N and I have to say I didn't expect it to be so good. I heard some rumors about it freezing but I have not seen something like that so far. I guess you need to have a good Internet connection which makes sense.
All channels are running smoothly, with good picture and sound quality, and the changing of channels is fast too. However if any of you have not visited the App Market, you're missing more than 50% of the device. There are apps there that add more channels to your device, like the XBMC and others like PopcornTime where you can watch even new movies that still play in cinema.

In conclusion, personally I am very happy with this device. I find it a good value for money and would recommend to everyone.