Who said all WordPress.com blogs have to look the same? Who said you cannot customize your theme unless you’re running self-hosted WordPress? WordPress.com had the Custom Design upgrade for quite some time now, and now it’s suited and booted with CSS3 support: animation, gradients, shadows, transforms and a bunch of other stuff.
You can even make your non-responsive theme into a responsive one, with media queries! Perhaps then share your CSS via the forums with the other “dot com” members.
The CSS editor itself has been upgraded too! Now that we’re using Ace, it’s just like having a desktop code editor in the browser: syntax coloring, auto-indentation, and immediate feedback on the validity of the CSS you’re writing are just a few of its features.
The WordPress.com Custom CSS plugin for self-hosted WordPress users might be getting the updates too, although that’s less exciting, since you were able to edit CSS anyway. A good use case, however, is a multisite environment with no access to sources — the Safe CSS plugin will make sure nobody’s doing anything fuzzy ;)