I favor the 48GX with several modifications. I have a library that gives me 5 stack lines, but also shows a symbolic representation. In other words, typing "5 6 /" is represented as "5/6" rather than a decimal equivalent. If you multiply that by 2, my calculator maintains the symbolic representation as "(5/6)*2". By retaining values as symbolic representation for as long as possible, when you finally evaluate, it will result in "5/3". This is great for when things cancel out and it allows me to carry precision further since I'm not working with approximations. I can also request the decimal representation at any time. This is what no other calculator app is giving me.