What issue do you usually have when you use ⌘+`? I haven't had any problems.
Also, the Z-ordering of windows seems really odd. If you have multiple windows open from two apps, and you ⌘+` between them, sometimes all of App A windows are brought to the front and App B windows are hidden. Other times only one App A window is brought up. Meanwhile, if you have App C chilling on a different monitor, it may or may not disappear at random.
Even if it worked as intended, it would be flawed when compared with Alt+Tab on windows.
Is there some company edict, or cultural pressure that discourages it ? I don't see how any of these issues could have survived early-alpha (of Lion, and ML, and Mav., etc.)