I have been using CSS for many years now, and I have always been a \'percentage\' kind of guy, as in I always define heights and widths using percentages as opposed to pixel
I use pixels on my website and I keep a maximum width of 1000px. My website displays properly on my 11" netbook, however does not do very well with mobile devices, but that is what this is for:
I find developing websites in percentages very time intensive, having to consider all re-sizing events, such as:
overflow:scroll;
Pixels and percentages both have their perks, but I would say that pixels would be a better choice because of precision, reliability, and is easier to develop. Also another thing to consider are pixels and percentages for fonts. Here is my rule of thumb:
If you have people that may need to enlarge the font it is always better to use percentages for the font.