Based on the AnandTech and Tom's Hardware reviews, the 840 Pro fairs much better on benchmarks and real-life simulations than what is shown in this review(which isn't bad). When I first noticed the reviews I noted not only how many times it came in ahead of the other drives, but how much better it did than the previous gen 830. That is what made me decide to pick one up in a few months. As long as the same rock-solid reliability is there, the performance increase over the 830 makes it a no-brainer for me.
Here is a thread on the 840 Pro to go along with this one(if it's ok) Samsung 840 Pro SSD!