In the 15 years since I first used a Mac, I've sent text and photographs in every concievable file format from Macs to print services, large CMYK presses, individual end users with bubblejets, et - and I've never had a rejection issue because of a platform incapatability.
That's a piss-poor printing service if they can't accommodate the industry-standard platform for most graphic arts and imaging fields.
What kind of a creative/ design firm doesn't run primarily on Macs in the first place?

Are they run by the Texas school board?

Windows 7 and Photoshop CS4 do not get along well (takes forever to open and save files, poor support of brush and pattern palates), although that may be an idiosyncrasy of my workstation.
