I had been using gold for walls and elixir for troops anyway, so, in reality, the change didn't matter THAT much, to me at least.
With the elixir collectors and mines each needing gold or elixir for the upgrades, and each making what's needed to buy the other's upgrades, and a giant costing 7 million elixir...and all the wall and $/E upgrades needing a builder, my walls are going to be coasting for a while.
With the new gold mines cranking out 3,500/hr instead of 3,000/hr, that's 7 times 500 x 24 = 84,000 gold a day more that can be used for walls later, etc.
They might upgrade canons and wizard towers and mortars, etc one day as well, add an upgrade level to DE or to the Lab or spell factory, and so forth...so, I'm SURE the added production rates will be handy.
I know that before the capacity increase, after a war, I was out of elixir anyway...I'd be waiting on the collectors to get troops training for attack #2, etc.
ONE L4 Dragon is 42,000 elixir to train, an L5 PEKKA is 50k, even an L6 Balloon is 4,500 to train, etc...these things slurp that stuff down in a serious fashion. The Inferno Towers and X-Bows eat elixir and get "reloaded", the traps and bombs at the max levels are even expensive to reset.
I think reservoir capacities might be the next upgrade, because things are getting so expensive that their max capacity is being hit to save enough to buy one upgrade, etc. I'm at L25 Royals, and, to get my Queen to L26, one Level, is another 130,000 DARK Elixir, the King is another 120k DE to go from L25 to L26. The largest reservoir only HOLDS 200k, not enough to save enough for both, and by the time it gets to L40, barely enough for 1 of them to go one level.
The gold/elixir storages max at 8 mill, and, for example, a max giant is 7 million all by itself...so if the NEXT giant, or PEKKA, etc, is going to be over 8 mill, there's no where to pay it FROM, unless they add a storage unit, or, add to their capacity, etc.
It would be nice if they made it so you can do payments with SOME of one and SOME from another too...so, lets say you had 600 k of gold and 400k of elixir, you could combine them to buy one 1 mil item, etc.