At the time I started using it, I was working with version 0.4.1, and as anyone with some Dojo experience can attest, it's a far cry from where the 0.9 and and later branches ended up. I've since upgraded to 0.4.3, but porting everything over to the 1.0 branch would have taken about as much time as moving over to a completely different library. The 0.9+ branches also officially did not support Safari 2, which was a huge problem considering we're an all-Mac shop. It also meant that production-side adoptation was pretty much out of the question as it's a safe assumption that the majority of people using any software are drastically behind on their updates, if they ever even choose to perform them. For a company that makes most of its money by sales through the website, we just can't afford to exclude and entire sector of people like that.
With all that in mind, I decided I'd poke around and see what else was out there as a possible Dojo replacement. A couple months ago, a friend tipped me off to Mootools, which seemed like a nice mix of Prototype and the Scriptaculous animation library that was built on top of it. I had passed it on to my boss as something to check out but it was kind of left at that, though I did plan to learn it on my own time.
Of the two other programmers in the office, one had been using jQuery for about as long as I had been using Dojo while the other had just started to implement MooTools into another piece of software he had written. Since those two were already in out code base, they scored extra points and earned my attention over some of the other libraries.
Since MooTools was called for in the case of this particular animation, I spent a little time reading through the API and the Mootorial and picking apart some of the demos available on the MooTools site. To my surprise, it started to make sense very quickly; their API is extremely well put together (with a few fringe exceptions), I found the code and syntax very easy to comprehend, and best of all, I managed to get the animation working in only a few hours having never worked with the library in the past.
The point of this long-winded post is simply that I have become a huge MooTools fan, and if you have a project that would benefit from a well-documented, cross-browser library with some really easy animations and extremely useful functionality, you may too. Check it out, I think it'll be worth your time.
One note I want to make is that I wrote this before MooTools 1.2 was released. For the record, I love the changes that were made; it's much faster, there are a lot of cool tweaks that make it easier to use and it adds a lot of very useful new methods. That said, I think their new documentation page and demos page are just terrible! In addition, they've completely disabled their forums in favor of Google Groups, which means any old discussions and examples now only live in Google's cache despite them coming up in their search very often. Those of you look for 1.11 docs and demos, see here and here, respectively.