I absolutely agree with Chip on this!
I also struggled to figure out how to get the free option at first, and had to actually read the text (heaven forbid)
Seeing that it is part of the core of a FREE piece of software, it should be totally free and enabled by default. The first time it launches it should get a free akismet key from their server. No setting up required!
If they want to go this route, then it should be removed from core IMMEDIATELY!

just my opinion, but I am now actively looking for good alternatives for future clients.