I faced situation of global site redesign (not appearance, but code architecture and underlying technologies). Website has about 135 000 visitors everyday. And it's crucial to make right decision now.
I had no experience of using LESS and CSS3PIE on such big projects before. Maybe some of you can predict some trouble which I can run into using technologies mentioned above. I would like to know advantages and drawbacks.
Isn't it better to use old tested and reliable methods like sprites for round corner buttons with shadows and gradients? I look at http://zappos.com. They just degrade gracefully in IE and don't use CSS3PIE.
I would avoid using CSS3Pie for production sites. In my experience, the higher the number of CSS3Pie-rendered elements on the page, the worse IE8/9 will perform.
Specifically, when I was using IE9 with an IE8 document mode, and with at least 2 elements rendered using CSS3Pie (using border-radius and linear-gradient), I observed a noticeable lag when scrolling the browser window. That is, I would try and scroll down the page, and the scroll bar would take a couple of seconds to "catch up" with the mouse pointer.
As soon as I switched CSS3Pie off, no lag when scrolling was observed. The same applies for IE8 in my experience.