Congratulations to the Octopart team for the fantastic work! For those wanting to try out javascriptMVC3.0 here's where you can get it: http://github.com/pinhook/framework
Originally I wanted to write it in Cappuccino and I actually started learning Cappuccino for that purpose. However, I had used JavascriptMVC for a previous project and in the interest of speed I decided to go with that. Also, I was developing our API at the same time I was writing the Part Browser and I felt more comfortable in JavaScript than Objective-J.
I think Cappuccino is great though... It seems like Atlas is a killer feature and I think it will be a must-have for UIs that are more sophisticated than the Part Browser. Every time I had to build a UI element from scratch I wished I had access to Cappuccino widgets.
Incidentally, I highly recommend JavaScriptMVC. It's an incredibly powerful micro-framework that is excellent for small projects but also scales extremely well to large projects. I basically hated javascript until I started using JavascriptMVC now I think programming in javascript is actually pretty fun.
I think the magnifying glass is perfectly acceptable here. I think the "filter" icon is much less recognizable to the majority of users. (case in point, the author of the app hasn't heard of it).
Some things would be improved with more attention to accessibility. Ext.tree.TreePanel, for instance, allows keyboard navigation out of the box. In a similar vein, the results grid doesn't allow row selection/keyboard navigation (ref. Ext.grid.RowSelectionModel).
JMVC doesn't provide packaged widgets (though it is starting to). It's about providing a middle layer (above jQuery, less than customizable widgets) to build customized apps that are as light as possible.
