I am patiently waiting for YUI3 to finally reach the feature level of YUI2. I've used version 2 on a few projects and it was a pleasant experience all-in-all.

I am patiently waiting for YUI3 to finally reach the feature level of YUI2. I've used version 2 on a few projects and it was a pleasant experience all-in-all. The only downsides were it was too heavy and too verbose. I often resort to JQuery when i need DOM manipulation because its nowhere near as verbose as YUI2. As for the too-heavy thing, it was a compromise because it provides one of the richest widgets in all JS libs out there.(plus YUI3's module system is supposed to help)