This works better in 10.5 Leopard than 10.6 Snow Leopard. As John Siracusa points out on Page 21 of his Snow Leopard review, Apple dropped the ball (and actually regressed) on updating some standard controls for resolution independence.

http://arstechnica.com/apple/reviews/2009/08/mac-os-x-10-6.ars/21

One other point, if this is for use in print, get a huge monitor and make the scaling factor an integral multiple (such as 2.0 times normal). Most speculation is that Apple never followed through on resolution independence because bitmaps at x1.5 and x1.25 will develop jaggies without including a huge number of special resolution cases.

But If this is for print, it may be worth your time to use exact multiples of the native interface. Yes, that requires a huge display. For example a 27" 2560x1440 iMac screenshot will only give you the information that could be displayed on a 1280 x 720 display (albeit at twice the resolution).