Not really, because it won't allow you to serve an MS compitable css page.

IE conditional comments solve that problem.

What's wrong with it? Unlike user agent sniffing, it works properly.

Oh? So how do I use it to detect which box model to use in my CSS?

How do I use it to detect whether I can use gradients?

And if you're just thinking about javascript, I've ran into a few text manipulation functions that always returned "not implemented". But hey, sniffer says they're there!

edit: Oh, and there's still plenty of html fun, too. How does your browser support <video>? <thead>? <svg>? I'm guessing the answer starts with "javascript".

I think the GP was referring to weeping with joy.

People don't wring their hands with joy.

They wrung their hands of user agent sniffing and wept for joy.

Oh, in that case, carry on!