ExpressionEngine is a CMS by the EllisLab Network, based on my beloved CodeIgniter. All I can tell you is based on the free core version, because I wouldn’t pay 100$ for the personal version, or even 250$ on the commercial version.
So, what is included in the core version? It contains the ExpressionEngine Core System and a weblog module with spam-prevention, statistics, trackbacks, XML-RPC posting along other usual features, such as comments, emoticons, rss feeds, and a search. Nothing special yet. But what is missing? A static pages feature (I think you could hack around that quite easily, but that’s another thing)
So is it worth trying out? There are some cool sites running EE, such as Subtraction.com and Veerle’s Blog, but is it also the best system for you (as long as you won’t pay)? In my opinion: No. Why? There is no open-source community behind it. Open-Source is so great and there are countless ways to benefit from it. Open-Source it the way to go and so such “Get-a-core-version-free…250-bucks-plz-if-you-want-to-make-money” business model. Yes, you have to buy the 250 bucks version if you want to make money with your site or use it in any commercial way.
My conclusion: ExpressionEngine? Nah.