Whimsically flipping flags leads to random inexplicable browser misbehavior a week from now after you've forgotten you changed something.

The reason these flags are off by default is because they have consequences: e.g. pipelining causes random HTTP timeouts if any proxy between you and your destination doesn't understand it. The GPU stuff will all be on by default once it works reliably.

Turn these sorts of experiments on temporarily to see if they affect a page you're working on, sure, but don't think that you're making your browser better by leaving them on.