I'm not nostalgic about the old, low-resolution monitors though. The content in those design fits into 630/700 pixel wide columns and the 11 pixel text in Orchid Beauty looks tiny on my screen!
It is not only the text size. It is also the low contrast. Add to that the fixed size layout, the orchids in the titles, the images replacing the titles (albeit with a proper fallback), the unmotivated plus-icon in the list…
Those old designs were great in the past to show what is possible, but now they are a reminder of the long way web design has behind.
I think relative font-sizing with "em" and "rem" [1] is a popular and good choice these days. "em" has been popular since 2004 after an article by Rutter [2].
IE9- (and Android 1.6-) didn't scale/zoom well when the font was set in px. But using px was widespread despite these (and other) cons because it was easy, reliable and consistent to implement across browsers. [3]
Pt (point type) are only for printer style sheets [4], not screen style sheets. Using them for screen styles is not-done and doesn't make much sense. [5]
That wouldn't help. Without wanting to go too deep into OT-territory:
Even if the DPI could be known (and afaik normally it isn't, it is just set to a value) and it would be possible to convert in into real inches (btw, I have no idea how big that is in real units) to be displayed on a monitor, how would a designer know how big any element, even text, should be? It depends on the available space, which depends on the size of the monitor/the size of the window.
To think about how absurd that would be, try to find a situation where someone would say "this heading should be 2 cm tall".
px as size lead to the same problem with the available space, but they at least correspond to the resolution.
[0] http://www.csszengarden.com/?cssfile=/211/211.css [1] http://www.csszengarden.com/?cssfile=/213/213.css