The RAM resident stuff is still useful, both at a lower level, but also for those of us creating applications that can live entirely in memory. A web site I did recently is careful to ensure that the entire primary data set can fit in memory, and for that site everything he wrote is still perfectly valid.
In fact, for very high performing websites you try to ensure that at least most of your requests come from memory rather than disk, which makes Knuth's stuff more important than ever. If you can't do it in RAM then you'd better have a lot of spindles!
I upgraded machines, and my new box already happened to have OO on it, so I gave it a go before deciding to buy a new copy of office.
OO 2.4 and now 3 has performed well for me in the past year - I've yet to have a document a client has sent fail to open. On the odd occasion it looked odd, I used the free word/excel viewer to open the documents (which confirmed they were broken - it looked odd there too). Note I only really deal with Word and Excel documents.
Really, it'll just depend on whether there are any specific must-haves for you in Office - for me there were none.
Without life, Biology itself would be impossible.