Would be nice to see how DDR4 compares with DDR3 - afterall you can buy mobos that support an i7-6700K and DDR3 - is DDR4 even worth getting (e.g. if you already have perfectly good DDR3 RAM and want to upgrade the CPU, do you get a DDR4 mobo and spend extra on new RAM or go for a DDR3 Skylake mobo and keep your old RAM)?
yes its worth it, lets be clear, im on ddr2 right now so ill give you my perspective on it.
i used my 8gb ddr2 system like i had 16-24gb of ram, and everything constantly went to page... you know how expensive going higher than 8gb of ram on a ddr2 system is? till recently it was around 100$ a stick, and you needed 4, had i went ddr3 instead of a ddr2 motherboard to save some money, i could have 32gb of ram and literally never have to worry about ram for the next few years, but i went ddr2 to save some money.
i got lucky and found someone in china selling 4gb sticks of ddr2 for cheap as hell, so i got my 16gb, but i still hit 95% use fairly easily...
at some point ddr4 will out pace ddr3 with even the cheap models, and at some point the size of the ram will go up to the point you could turn it into a ram drive and still have ram to spare...
its worth going ddr4 just so you arent left behind...
also, lets not kid ourselvs, the last real reason to upgrade your computer was when you had a core2quad/duo or a phenom II 6x/4x/3x/2x and sandybridge came out, sense then there is been next to no reason to upgrade for a normal user, and with a ddr4 system, baring hardware failure, there will likely not be a reason to upgrade again for 6 years, so you may as well go ddr4