Yes. 54Mbs will stream HD movies. (haven't tried bluray yet)
They actuall will buffer several minutes ahead of what your watching.
If network traffic is high it will buffer more.
The result is you can watch glitch free until the buffer is empty then movie stops until buffer is full and off you go again. Only time I've had buffer run out is when the web site is overloaded or very slow and when I skip ahead to a different scene.
You may want to keep the Wife and Kids from downloading with the wireless while your watching movies. if they complain then upgrade to a faster model.