Darren Hobbs wrote about one of my favorite topics: Tiny Types. I call them abstract data type, but I like Darren's name better. The idea is the same. I think it's just good design. I once thought that tiny objects were too much as well. But, I now think tiny objects is the only way to go.
Tiny objects make unit testing easier, aid in reuse, stop duplication dead, provide for better messages when things do break, puts functionality closer to where it is used, and I could go on all night. The amazing thing is at first I started to use tiny objects to put constraint checking in so that it didn't get propagated everywhere. But, something strange happened. These tiny objects started to take on more functionality and have real protocols beyond just get and set of their values.
I think tiny objects are even more important in dynamic languages than in Java. They can make stupid programming errors easy to find and correct. Also, your functionality is spread across several single responsibility objects working in concert to provide complexity.
Tiny objects are good design period.