Looking back at pass papers most of them call for using calculators - this tends to be true for extension 1 as well, although it generally has one question you need it for (+ combinations coming to think to it)
I used mine, but only to check some trig things and a log a think = nothing i shouldn't been able to do in my head
I use the calculator to convert decimals into fractions, and do powers, and add stuff quicker. It's simply a tool to get the job done quicker and more reliably.