I too have experienced buffering problems with netflix, even though i have ultra high speed internet.
I had a samsung wireless blu-ray player connected to net via wireless. Buffering stalls were so severe that I could never
watch anything on netflix. Much of the time, the program would not even load, let alone stream well.

I have troubleshooted the issue, and I have concluded that the bottleneck is mainly the result of one issue
not typically blamed for these problems: PROCESSING POWER!

A lot wireless blu-ray players have TERRIBLE processing power, and this can be a severe bottleneck to streaming
data. If you want to stream HD, do yourself a favor and get a dedicated streaming device, like a Roku device.

Second, if you have the option, use a direct Ethernet connection whenever possible. However, the wireless on the roku
well too, although not as good as ethernet.

Once I made these switches, my streaming became lightning fast with no buffering issues.

Hope this helps some folks.