Except I'm in trouble when I need to use the 50/50 grid, or even a 3 column grid because JQM appears to mark up the grids dynamically and I now have a table with column1 width: 65%, column2 width: 35%, and column3 width: 33%... which of course wraps the content.
Any plans to support defining unequal widths for grids?
Alternatively can someone point me to a colspan-like feature? I could just as easily get my content layout looking right by specifying a 3 column grid and use a colspan=2.
Your suggested CSS override is the absolute minimum it seems you can "get away" with to get the effect you want, but as you pointed out, it'll affect all other places you want to use the default grid behavior. If jQuery Mobile loads another page into the existing DOM, it won't reload the CSS and you'll be stuck with the widths you've overridden in the other page.
You might be better off making your CSS more specific, for instance add more classes to the div's you want to tweak - say "main" for the wide column and "side" for the narrow one. Then protect yourself against nested grids by using CSS child selectors and the additional classes - that should target precisely the columns you want to tweak and no others: