alt Hacker NewsMy favorite feature of 3270/5250-style keyboard layouts is the separate carriage return and Enter keys, allowing for multiline text entry without special handling to avoid conflicts with the command to signify that input is complete.
With only a single combined Enter/Return key, it's hard to remember in any given context whether Shift+Enter or Control+Enter will open up a new line instead of immediately sending a message, dismissing a dialog box, completing input into a particular spreadsheet cell, editable filename, text object in a drawing program, etc., or whether I need to copy/paste a line break from another application because no such shortcut exists at all.
The software I've used has been pretty consistent about Shift+Enter meaning "new line without triggering the Enter key action" and Ctrl+Enter meaning "action" (send the message, go to the next field, etc). The behavior of the Enter key varies from program to program, but I have yet to find a program where Shift+Enter triggered an action while Ctrl+Enter did not. Which software are you using where Shift+Enter triggers an action?
(I do agree that it's hard to remember what Enter is going to do, of course. It's just Shift+Enter where my experience differs from yours).