[Cottser]

I've been able to print 3x5 cards with no problems. Go to File > Page Setup, then Paper Size > Manage Custom Sizes. Set up your 3x5 cards there. Now, if you're printing from OmniFocus and want Index Cards, choose your custom made size from the Paper Size menu in Page Setup.

While I agree pagebreaks and more control will certainly be welcome, I'm just glad that it works. I usually turn off start/due/duration columns so that the task column isn't so squashed.