As a University Lecturer, I found Power Point extremely useful.

I use Open Office as my normal Office Package and have done since just before I retired. I have found it very capable and no slower than MS Office on any computer I have owned - at least at the time I had both. Since going over to Linux as my OS, I no longer have MS Word available and I do not miss it.

I think the first release of Libre Office was essentially Open Office with the updates that were being worked on at the time Oracle took over Sun. I have Libre Office on my netbook but have not made a lot of use of it as I don't use the netbook that much for Office type tasks. What I have seen it is essentially the same interface as OO so if you are used to that you will not really need to learn anything new.