[corecoder]

You're right, I just opened a 1.2gb file (obtained with base64 -b 60) in fundamental mode, and it actually works decently enough.

I tried the same with Sublime Text: it took a long while to open the file but, once opened, navigating the file was very slick, I could scroll from top to end and vice versa in a breeze, so I would say that Sublime Text still wins this one.

[edited to clarify: Emacs opened the file in just a few seconds, but then going to the end of the buffer, to the beginning, to line 100.000 is quite slow.]

[mafm]

Large files seem fine in emacs as long as the lines are not too long. A 100MB file is no problem if there are less than a couple of hundred characters per line. If the average line is 2K characters, emacs will be unusable.