Apple has famous typographic literacy and graphic design taste.
But Microsoft, with a far worse reputation for taste, has employed famous typographers for each major release of its OS, contributing serious, important typefaces. Vista included Lucas de Groot's Calibri and Consolas, for instance.
Even Palm, a relatively minor company, has a real face commissioned for the Pre.
But Apple's new typeface is just a tweak of Bitstream Vera Sans Mono, Linux's open source monospace sans?
The major difference, as I see it, is that Apple includes fonts that are good for publishing, and Microsoft includes fonts that are good for reading on a screen. For example, Consolas is designed for a screen with sub-pixel rendering.
I think this difference is apparent in how fonts are rendered on OS X and Windows, i.e. Windows "snaps" fonts to pixel grids for readability.
"Just a tweak" minimizes the work necessary to make typefaces (especially monospaced typefaces) produce good results. The hinting in Menlo seems to produce really good on-screen results on my Mac; preferable to Consolas, Liberation, BVSM, Pragmata, etc.
It's a different kind of work. I've purchased several typefaces with beautiful letterforms that are useless for coding on my mac because they are not hinted or hinted poorly. A couple more have really bad metrics that the "height"/"width" sliders can't really compensate for in the terminal.
Zapfino is the most immediate counter that comes to mind. Monaco was for decades the best monospaced font going. My Mac has Futura on it (a fantastically influential and important font that I happen to dislike aesthetically a great deal), Gill Sans (probably the best sans serif body font), Hoefler Text (gorgeous), Optima and Palatino, for starters.
You don't need to commission new fonts if you have the good taste to buy the distribution rights for excellent existing fonts.
The only fonts in that list that Apple commissioned are Monaco and Hoefler Text, both from more than ten years ago.
I'm not complaining that Apple ships with a poor selection of fonts. I'm complaining that despite the heritage, they don't appear to be innovating with typography at all anymore. Microsoft is simply crushing them on this front.
You're confused. Microsoft isn't innovating here either. They're paying someone to innovate. That's why it's called "commission".
If Apple employed great type designers and was giving them nothing to do, that'd be a problem. But there's been no shortage of great font releases without Apple's patronage -- and all these releases can be installed on a Mac. So what's your real problem here?
Menlo is nice. I use it as the default in Xcode, Terminal, and Safari under 10.6. It looks to have been tweaked from Bitstream Vera Sans for Quartz's anti-aliasing—like Consolas was tweaked from TheSansMono for Cleartype. The letter forms in TheSansMono are the most beautiful—if you're printing a program listing or samples for a book buy and use TheSansMono—Consolas is the sharpest, easiest to read on Windows LCDs, but looks funny on Macs; Menlo is clearer and easier to read on Macs than Consolas. If you want to use the same font set on Mac, Windows, Linux, et al, the Liberation fonts are the best plan; Liberation Mono is pretty, consistent, and doesn't morph too much between renderers.
The Droid family from Ascender, which Google commissioned for Android is uniformly excellent, renders well everywhere I've seen it and is Apache Licensed. I'm currently using 'Droid Sans' as a system UI font (on Linux) and 'Droid Sans Mono' for coding, terminals, etc... In fact I've just aliased the linux 'sans', 'mono', etc... to the appropriate Droid face.
I think Droid and Liberation are siblings, from the same designer & foundry. Liberation has more variations (italic, bold italic) and more "flourishes" (like in the uppercase Q, lowercase a and what not).
Compare to Prelude, an entire sans serif family Palm commissioned from Font Bureau: http://typophile.com/node/58935
First Microsoft, now Palm; Apple, you really need to raise your game here.