Any drawbacks?
none. did it a while ago, it makes a big difference. you have to restart firefox (close all open windows) and restart it to see the dif
There are probably still websites that get confused by pipelining, which is why they don't turn it on by default. So if you run into problems after trying this, you should probably just go change the settings back. But if you don't have any problems, it will make your life a lot faster having it turned on.
These have been my settings for months. I'm not aware of any drawback.
There's always a tradeoff, or else this would be the default setting. Some websites will see a massive speedup, some will actually load slower, and for most, the improvement is not all that significant. Try it out and see how it works for you, though.