The effect is not lost at all. It's Fitts's Law: http://en.wikipedia.org/wiki/Fitts%27s_law -- the Mile High Menu Bar is still a mile high on a 1920x1080 display. http://joelonsoftware.com/uibook/chapters/fog0000000063.html
With Unity, though, the global menu bar on a large desktop is "a mile high, a mile away, and invisible". You get to guess where you should be aiming.
Are you really arguing that hitting a target you can't see is easier than a target you can see?
All that said, I do prefer Unity over other options on my netbook. The savings in real estate is well worth the marginal cost in usability. I don't use the menu bar much, anyway.
That last bit is probably Unity's saving grace: most apps used by most people are no longer designed with the menus as the primary interface.
Since they're less used, it makes sense to optimize screen use by tucking them away at the top of the screen.
I wouldn't at all mind if the menu bar had an auto-hide mode, though. Actually, what I'd like is a partial auto-hide. Tuck away over to the top left, with only the window widgets and the indicators showing. I'd gain a line or two in any editor or term on the right side of the screen.
To test your intuition (by quoting one of Tog's favorite puzzles): Name the five points on the screen that are the easiest to hit with the mouse.
On Macs, fer love of Pete, the Mile High Menu ... is on the other display.
Menus just f@cking suck anyway. I've canned my browser menus via Vimperator (on Firefox / Iceweasel). Sure, I'm a power user and I know what I want to do and I've got finger memory five miles deep (plus command completion). So suck on that teat.
Fipp's Law optimizes for one case: mouse navigation. Sure, it's nice to have a big fat landing zone, when you need it. But often you don't, and the optimization unambiguously and indisputably breaks numerous other optimizations. Which frankly I care a whole f@ck of a lot more for.
We're talking about desktop (or large laptop) displays here. For tablets and small-factor handhelds, there are other considerations. Which is why UI design is complicated and a task and disipline worthy of research and nuanced understanding.
The 1980s were 30 years ago. Go ahead and pop up a 512x342 window on your desktop. On my not-extravagant dual-head display, I can stack those up 6.5 across and three high. With window decorations.
Y'know, I credit Jobs with some good stuff, and he was nothing if not persistent in believing what he believed in. But some things really have to go.
Use the software.
How does that do anything but confirm the GP's point, that it's dumb to place a menu bar potentially thousands of pixels away from the window it applies to?
This is also why pie menus have improved time and error rates over linear menus: linear menu targets are very small, and increasing distances away from the cursor, but the pie menu items all start out adjacent to the cursor, and extend all the way out to the screen edge, so you can trade off increased distance of movement for increased target size. The target area of the pie-slice shaped wedges get wider and wider as you move out further away from the menu center. (I don't mean they dynamically change size as you move, I mean that as you move out, you're in a much larger part of the slice. So with a four-item pie menu, each target area gets about 1/4 of the screen real estate, and you can keep moving the mouse even further when you hit the edge and still be in the same target slice.) Pie menus also minimize the distance, but around the center, the targets are at their smallest, but you can always move out further to get more "leverage" and directional accuracy.
That menu bar is effectively a billion pixels tall. You can throw the mouse pointer to the top of the screen and only concentrate on accurate horizontal positioning, since the mouse will not leave the top edge.
Putting the menu bar at the top sells out the distance side of the function to dramatically increase the target size.
On multiple monitors, the menu can be 1 or more monitors away from your app window. It might not just be up at the top of the screen, it might be up at the top of 1 screen over and two up.