Me too. Love my DM42. I also have an HP35s and two HP12Cs still on the batteries they were rocking over 10 years ago when I used them daily in my finance days.

To answer the op's question, any RPN calculator is wildly better than the default calculators on things like iOS once you take the time to learn to use it[1]. If you want a good calculator app, Thomas Okken's free42 is a great, free HP42S emulator which runs on iOS. I still prefer a physical calculator (eg the swissmicros has more screen space so you can see 4 lines of stack and dedicated function buttons) but it's much better than the default.

[1] Great support for complex numbers in polar or rectangular form, fewer keypresses for multi-step operations, no ambiguity (whatsoever) about operator order without any need for parentheses, vast number of memory slots (not just one), the ability to write a program to do anything you can do manually on the calculator so you can automate anything you do frequently, numerical integration and root finding etc etc there are many many benefits.