If you're a unix sysadmin or a full-time hacker, you can justify the cost in time and effort of learning and memorizing all this stuff. In fact, you'd be foolish not to. But there are a lot of people who don't spend all day in a terminal. Nevertheless, they frequently need the unix terminal to get something done. A tool like TermKit could be a huge boost for those people allowing them to bootstrap their knowledge without having to dive into the deep end all at once.
There are legions of people out there who are smart enough to learn some bits of unix if only the learning curve wasn't a sheer brick wall. If you need evidence that man pages and "-h" don't cut it, start typing common unix commands into google (xargs, tar, grep, etc...) and you'll almost always find one of the top suggestions is "command_name examples" or something like that. Why is that? My grandma isn't trying to use "xargs" I assure you. Someone with enough knowledge of the unix command prompt to know they need xargs reads a man page and they still don't know how the hell to use the command properly. That's a usability problem and there are modern ways to help with it (as is demonstrated by all the things IDE's do to help programmers all the time).
I'm really excited to see where this goes. There are all sorts of possibilities it opens up.