Designers were never Apple's target demographic, even though Apple and Adobe started the desktop publishing revolution. Education and home use have always been the Mac's target demographic.

Ofcourse, the creative industry has always preferred Macs, and they still do. That's why it's the designer's platform, not because Apple targets them.

As for Apple's displays: you're right, they're not as good as high-end monitors from Samsung, Eizo or Barco. Apple's displays are not made for print designers, they're made for multimedia. This has been the case ever since Apple switched from CRT to LCD. However, the price is right: $999 for a 27" screen with LED backlighting and IPS is hard to beat.

As for Photoshop performance on Mac vs Windows: are you using an older version of Photoshop for Mac? Those weren't 64-bit, didn't utilize the GPU and didn't make use of multiple cores well. Try CS5 on Mac, it's stable and fast.