I might actually get a Tumbler too just to try it out, but a friend (and godparent to my children, Hi Irene!) sent me this link:
http://www.blackweb20.com/2010/10/05/tumblr-vs-blogger-vs-wordpress-what-you-should-know/#
I think it's funny that the author isn't using any of the three he reviews to write this :) Oh, and it's actually Irene's fault that this blog exists in the first place, so we can all blame her for this.