I agree with you.
Having a unified memory is a nice thing, but i expect it will only make a difference in something like the PS4, where you can target a specific architecture, which has GDDR5 as main memory, and doesn't have a discrete GPU. These two points are relevant: if you have "normal" DDR3 you loose a lot more than you gain by having UMA, and this will not change a thing in discrete GPUs because the PCIe bus is going to always be in the way of the GPU accessing main memory.
I think it is more a "nice to have" than a big step forward. The difficulty in programing GPUs lies in the different algorithms one must employ, and while having to copy memory back and forth between the CPU and GPU is a nuisance and something to be avoided, that usually isn't a dealbreaker, though i admit it is useful in some situations.