It reloads the whole page and does consume memory resources. Plus the blink every 5 seconds is somewhat distracting; however, I like seeing the chart I'm used to refresh so quickly. I had that up this morning with E*Trade Pro so I could "fill in the blanks" of where the price was heading during the 5 seconds.
It's a bit kludgy, but very workable for me. More sophisticated and experienced traders might really be distracted or hate the setup. I guess it's an evolutionary process for me.
If you find a way to get 5 second refreshes without refreshing the whole page, please let me know! Thanks!