Actually, I have a family member who is entirely blind, so I have plenty of experience with how they deal with (and don't deal with) the internet. Recaptcha is not perfect, nobody is claiming it. However, it is functional. Most spammers are not going to spend the time and money to get past captcha, a few will but most will not.
The point is more this: It isn't any less effective in dealing with spam as compared to Akismet, so it's disappointing that something is grandfathered in while not being the optimum solution.
As for using it for free, if you have a popular site (at least popular with the spammers) you will blow past the volume levels very quickly that will make it say that you need a commercial license. The first level of license is insufficient for the most part, meaning that you have to pay on a volume level. This isn't for a service you need, but to protect against a weakness and deficiency of how wordpress handles spam.
It's funny. I came to realize a while back that wordpress's problem of spam is exactly the same problem as why spam is such a problem in email: Overly permissive and easily manipulated systems, with default settings of wide open which invite, permit, and encourage spammers at all levels. The solutions generally put forward are like sandbags in a flood, a poor line of last defense for something you can't stop.
So the real solution is changing the core function and core functionality to better serve real users and to make it less appealing to spammers. WordPress installs are too easy of a target with default settings that encourage them. As an example, allowing people to post a comment based not on the name of the post (or it's permalink) but rather allowing them to use the postID, even if you are specifically not using postID in your blog. Ever wonder why your spam often attacks older posts? it's because they just aim at a random low post number and fire away. Often once they have one comment accepted, they will automatically add that post number and domain onto a list and come back to spam it again and again. Even if you decline the comment or mark it as spam, as long as it gets accepted on submission, they keep coming back. They exploit a weakness in the way wordpress approaches spam to make it easy for them to spam.