Not sure what your problem was. I just popped up a 91M log file I had sitting around in my emacs (a CVS build from about a year ago, somewhere on the 23.x line I think). It took about 7-8 seconds to come up (probably building the table of line numbers) and is perfectly snappy interactively. This is on a laptop with 2.5G of memory running Ubuntu Gutsy.
Ok. I thought I read something where somebody was furious because their thesis had grown large enough that suddenly Emacs couldn't load it (or process the LaTeX?). I'm pretty sure it was Emacs 20, though. I'm glad it's not the case anymore.
Serious question.