Depends on your use case. If you're going to be playing average games then you're likely fine with the stock CPU. If you're going to be playing a game that is optimized for quad core CPUs or doing a lot of CPU intensive desktop work then you could benefit from the upgrade.
A couple of things worth thinking about:
You can always upgrade the CPU later BUT it won't be covered under warranty and you have to be comfortable with the process. I think some folks will stay stock for now and upgrade when the warranty runs out if it makes sense (as the hardware will also be lagging behind current tech of the time).
Even if you have a faster CPU, the GPU will start to lag behind newer offerings and you won't be able to upgrade that. The point being that if you don't need it now, buying a faster CPU just in case might end up being a waste if the GPU won't play the games you want to play.
A bus station is where a bus stops. A train station is where a train stops. On my desk, I have a work station…