I’ve always had mixed feelings about Yahoo!.
I liked them in the earliest of days, when it was just a little directory of stuff on the www (as I remember calling it). I got fairly turned off when it became hugely successful, because of its “vibrant” esthetic and extremely commercial focus (ads everywhere!). I was curious when they acquired one of my favorite companies, Ludicorp/Flickr. I was scared when I saw Terry Semel present at Web 2.0, and he made it so clear what they saw as their role as an advertising company. I was impressed when I understood the diversity and richness of their business model (selling nikes for virtual avatars in online games? wow/sigh). I’ve somehow always felt slightly funny about their developer network promoting talks at technical conferences (not sure why!). When they bought good companies, the people behind them seemed to disappear behind the firewall. So, overall, wary.
This last little while I’ve been very impressed with what they’re doing on the web development front. Their YUI library is nice. Publishing and maintaining CSS stylesheets to help cross-browser design is a thoughtful touch. Their cheatsheets are an elegant combination of thoughtful content, smart page layout, and beautiful design (I immediately printed them and pasted them into my new notebook, only to have them be made obsolete the next day with a new release…). Their design patterns collection is a Good Thing for the web. I’m looking forward to playing with YUI more.
Luckily, as a user, neither I nor anyone else needs to pick one or the other (plug: Komodo 4 will ship with built-in support for both, among others!). With some caveats, it should be possible to cherry-pick the bits from these or other toolkits (yes, I know, prototype.js-based toolkits don’t play well with others often).
Now if someone could figure out how to make flash plugins play well with the event system, we’d really be onto something…