AlanG,
No, you are not the only one. Although I initially did not notice any breakup / buffering issues. This was based on my initial impression after activating my STB around noon (EST) on Monday of this week.
Since then, I have noticed that in the early evening hours (around 8 PM EST) there is some breakup (I have the German package). This is not the case in the morning, nor around noon time. It only occurs in the evening. This was not the case when I had OverseaTV.
Considering that I have a 15 Gb/s DL service from Cablevision (I have measured about 13-14 Gb/s using speedtest.net), I do not think that is the issue. It is either 1) higher internet traffic in the evening hours or 2) NexTV not being able to fully handle the capacity of the higher viewership during "prime" viewing hours.
I hope this issue will be resolved.