I second the motion... It was probably the first thing my users asked me when I showed them their shiny new toy. "So... you can't select text anymore? How am I supposed to copy this to here?" Most programs let users select text in grids, like Excel or InDesign (what my users are more accustomed to) - it's confusing to them that Ext grids don't, since they look so much like any other program. But enabling text selection isn't so hard in the CSS - my real problem is, even when you do that, selecting is *hard* - you end up selecting half of the text in the grid most of the time, depending on where you click to start selecting. You pretty much have to start from the right and select to the left - very unintuitive. I've been teaching them to double-click to select a word, that works pretty well for most purposes (some of them actually love it and never realized they could do that).
If anyone else is trying to convince difficult-to-please users to deal with this, double-click select is the way to go...