I've spent a couple of months with this guy, buying it just after it was released in the US. I've long been a fan of the 991EX, and the CW is quite a different beast in terms of UI and capabilities.
First off, this thing is an absolute beast! It is the most accurate and precise calculator that I own by far. I knew when I put the fx-115ES Plus 2nd Edition through its paces and watched it soundly beat the 991EX that the CW was going to be a leap in capability, but I had no idea how large that leap would be. Take a look at arcsin(arccos(arctan(tan(cos(sin(9)))))-9 in degree mode, which should equal 0 but never will if your calculator is solving it arithmetically. most calculators will give an answer in the range of 1x10^-6^ to 1x10^-9^. The CW's answer is 7.5528x10^-18^, doubling the number of accurate digits!
Another mind blowing one is it's integration abilities. One of my favorite tests is int(e^-x, 0, A) and finding the value for A where the integration breaks. The value should approach 1 as A increases, but because the calculator's algorithm for integrating is not exact it will reach a value for A where the answer is wrong because it starts ignoring smaller values of x. Most of my calculators can make it to A being four digits long before they decide that the answer is either 0 or they declare an error. The CW gets all the way to 2.55x10^9^ before it craps out. I was astounded!
As for the UI, limiting each button to a single shifted function is a double-edged sword. It irks me that I need to dig through a menu to find some pretty basic things like integrations and derivatives. At the same time, I'm approaching 50 and my eyesight is not what it used to be. I don't need to take off my glasses and squint at the keys to see what they do. I wasn't sure what I'd think of the round keys, but they feel great in use. I'm also disappointed that they removed the ability to perform simultaneous equations with the : symbol, but it was a feature that not many people even knew about, let alone used regularly.
The only improvement that the CW let me down with is it still lacks persistent memory. It has a lovely spreadsheet function that is made useless by forgetting all of the entered data as soon as you change functions or turn it off. The same thing goes for data in lists or the statistical apps. This is not a calculator to take out into the field and use while gathering data. It really is the only thing that has kept the fx-991 series from being the perfect scientific calculator. It's still close enough to be really impressive!
