Jalatext allows you to mark positions in a file, and rapidly move between them. You can also export all of the text between bookmarks, which is  handy when trying to extract a large segment of data. When combined with the regex (Regular Expression, and if you need a program like Jalatext, you either know what these are, or you need to learn) enabled search functionality, this can enable a lot of navigation shortcuts.

However,  I've had freezes with Jalatext when doing searches in large files. I've worked around this by reducing the size of the file segment I chose to use.

Jalatext also has the ability to save the file in a different encoding, a boon when moving huge files from one OS to another, or making them readable by newer or older programs than the ones that output them, a common occurrence.

On the negative side, Jalatext does not have any capacity to identify delimited files and to display the data in an easier-to-read format. Delimited (often comma or tab delimited) files are one of the most common types of huge files, and this would be a good feature for future expansion.

Jalatext does a specialized job and does it well, but it's a little bare-bones for the $30 price. The 30-day trial has no functionality restrictions, so that's ample time for anyone to test it out and draw their own conclusions.