I use a Windows machine for my "real" data (just beginning a migrate), but I use OpenOffice in preference to MS Office. Yes, it takes forever(well, not quite, but it can feel like it) to load, but, once loaded, it feels faster. I prefer it all round.
And as for the MS grammar checker: most of the things it brings up are wierd and some are just plain wrong. I don't know where the designer of that particular piece of software studied grammar but I don't think s/he was taking notice. It is a totally appalling piece of rubbish.