Funny you mention that. My partner has a 15" G4 PowerBook (matte, obviously) and I have a MacBook.
Outside on bright days, the PB's matte display completely washes out, making it impossible to read outside when the sun is overhead. If the sun is still rising or setting, he can reposition himself (i.e. face into the sun) with some success, but if the sun's "above", he has to go back inside.
With my MacBook, I just have to re-adjust the angle of my screen and I'm good to go. Zero washing out.
Indoors, there are situations where both screen types are great and situations where both screen types are poor. But generally speaking, any situation that causes a glossy screen to glare also causes a matte screen to wash out.
Just my US$.02.