This is an interesting subject in several ways.
You're right to go for something like this, in that it is a formalised training programme with a guaranteed outcome - that you'll be knowledgeable about the stated areas of ( what's known as ) Linux at the end of it.
Of tremendous importance is the social aspect. You'll be in contact with other human beings - the tutor and probably other participants. A great thing about the IT world is the scope for sharing problems, experiences, and ideas. It was good to read recently that the annual hackers conference at a west-coast American hotel is the best party that the hotel has all year, and they love the people going there. The hotel sells the most beer that they ever do at the conference, and everyone has a great time. That really is a strength of the UK Open University, that you get to meet other like-minded people in a similar way. Inspiration like that is worth a thousand magazine articles.
The prospectus is a good foundation for other OU courses - indeed it goes on to mention the BSc degree. This would obviously be far more expensive, but again after hard work it gives predictable results - and there are great summer schools which is party time again ! So it's a fun way to get qualified - or as you say, to simply learn some basics.
As to the price, in the commercial computing world, the cost of the course is at the low end of course prices. It may seem high to a private individual just wanting to gain knowledge, and I agree with what everyone else has said about other ways to do it. But you've signed up now, and I don't think that you've made a mistake in doing that.
Going back to the OU and prices, they have become more competitive now for us in the UK, because the central Government have withdrawn funding to academic institutions, who have had to up their course fees to that of the OU. People I talk to in my home town of Leominster tell me that they are considering OU courses instead of going to Worcester ( UK ) University, because the latter is going to start charging 5,000 pounds per course. Suddenly the OU starts to look attractive for the young people looking for their further education.
As regards the knowledge, the course material is a broad range, but nothing too specific. That allows you to keep your options open, and whether you just want a pastime at home, or to go on to study for a BSc, then it is a useful introduction. I have to say that to get a job in industry, you'd need to have something else to add to this course. Employers will be impressed that you can show an aptitude for learning the subject ( and socialising ) but they will also be looking for skills in web design, or database management, etc. You would have to be able to show an employer that you are going to go on to learn those, or perhaps actually study them, before going for a good IT career.
As others have said, I hope that the course is everything that you want it to be ! Good luck !