I get that slickgrid is unable to autosize columns like a standard HTML table because it doesn't know all of the possible values in the column before drawing the table (due to it's highly performant load-as-needed implementation).
However, once all of the rows are loaded and displayed on screen, is there any implementation that allows a user to double-click* on the column boundaries and have it resize to fit the already-loaded data? Sure this resize may not be perfect after loading additional rows, but my data (and I'd imagine many others data) is such that loading 50 rows at the outset is a good enough sample size to determine an appropriate width. And even if it's not, the user can always double-click again.
* Here is the description that Microsoft provides on how to do this within Excel: http://office.microsoft.com/en-us/excel-help/change-column-width-and-row-height-HP005198813.aspx#BMmouse. Read the third bullet that discusses double-clicking.
