I noticed the same on my new 15 inch anti-glare MacBook Pro. I used Firefox 4 and this issue clearly popped out on this site:
http://sage.ucsc.edu/~wgscott/xtal/wiki/index.php/Unixand_OS_X:_The_AbsoluteEssentials
If you have the problem, you can see it when scrolling up and down the page slowly. Fonts are dimming and brightening up. Theres some dashed lines and white table borders that also suffer this flickering.
I went to a market and tested other MacBooks with glossy screens. I used the same site for testing. I noticed flickering with all MacBook Pros (13",15" and 17"). There was no screen tearing, but I noticed later that it was because of Firefox 4. See:
http://support.mozilla.com/pa-IN/questions/806026.
Even the basic MacBook had a little flickering, but not so noticable or disturbing.
At home I plugged my HP LP2475w display in to my MacBook Pro and there's no flickering on that even with slow smooth scrolling. So I deduce that this is not caused by graphics card, but by the display itself.
This problem is not only limited to web browsers. You can reproduce the flickering by opening TextEdit on full screen, writing text so that scrolling is enabled and scrolling it up and down. If you are in dark room you can't miss it, the aluminium surface in front of the display is flashing in light. This flashing is not happening on my external display.
I have tried to change settings in System Preferences > Appearance, but it doesn't have any effect.
I expected to get a high quality display. I have never seen this kind of thing before. It's straining my eyes in dark environment. Is this normal on LCD displays?