Probably very subjective. I, for one, am still using Courier New as my main monospace font, especially for code, and actually prefer having typewriter-y "serifs". No other serif-y monospace I've found fitted.
I don't mind Consolas, and I like what is author using now (DejaVu Sans Mono), but their stance about varying reading experience depending on the OS makes me really, really devastated, because it just reflects a sad state of IT literacy and general adoption of basic philosophy of the web, which was built on premise that how content looks like depends both on author and user (through user agent) and fact that generic font family looks ugly is in other words defaults are bad combined with users have a bad taste and set bad default values.
As was said, we are supposed to express our preferences in (through) our (user) agent's preferences.
Most probably your browser will use four distinct fonts on this page, *all* of them (and more) you can define in your browser's or operating system's settings:
data:text/html,<p lang="ja">iii<code>iii</code><p lang="en">iii<code>iii</code>
It's sad that it is not a general knowledge.