Is it possible to do multi-line editing like Sublime Text but in Vim? I use both, and this was the feature that got me out of Terminal, but besides this I can't think of anything else offhand for what ST2 can do that Vim can't do.
Yes, Ctrl-v to enter visual-block mode, then move up or down to cover all lines where you want to make changes, then I{string}Esc to append a string at the cursor location on all lines.
I'm not sure exactly what you're looking for without knowing more what you mean by multi-line editing, but you can apply arbitrary commands (including inserts) to any set of lines.
Switches case on lines 4, 15:
:4,15 norm ~
Indents text and changes the first two words of ever line to "duck" from mark a to the end of the file
:'a,$ norm >>2cwduck
Prepends a # to every line of the visual selection