Badbonji
I'm guessing due to the higher latencies the first generation of DDR4 will be slower than the current best DDR3 modules.
Depends on what you mean by slower. It looks like they're starting DDR4 at 3000MT/s, so one stick of that will provide almost as much bandwidth as
dual channel DDR3-1600. Compared to enthusiast grade DDR3 it will probably benchmark slower, but there are hardly any computing tasks that are RAM bandwidth limited anyway, so in real terms you probably won't notice the difference (the same way that triple and quad channel DDR3 on s1366/2011 dosn't make any real difference). Plus as you keep adding DDR4 sticks you keep getting more bandwidth, so when we get it on mainstream platforms is will start making a huge difference fairly quickly.
Obviously the main thing that's currently bandwidth limited is IGP performance, particularly for AMD. A Kaveri platform with 2 sticks of DDR4-3000 will have half as much bandwidth again as the current dual channel DDR3-2133 setup, and with 3 sticks will have more than twice the bandwidth of the current setup. I guess in laptops it'll be even more noticable, because it's rare to get higher than DDR3-1600 in laptops, whereas by the looks of it Crucial will be doing DDR4-3000 SODIMMs up front.