Fair warning: I'm talking about the Linux version, not the Windows version that I suspect that you are downloading. I notice that the OOo downloads are 1.0.2 rather than the 1.1.1 that I use. I only used 1.0.2 for a bit and 1.1.1 is IMHO quite a bit better.
It's very good. Essentially it can do pretty much everything MSOffice does and then some. It isn't as polished as MSOffice and you'll find a couple of small irritations along the way. Importing .ppt presentations can take quite a while. Best not to expect it to be an MSOffice clone in terms of behavior or you'll be disappointed. OTOH it does have some features and tricks that MSOffice doesn't. Good luck!
And it doesn't cost 350 quid....