I've succesfully installed MSOffice 2007 in wine to try it out (the needed components are only Powerpoint, Word and Excel). so far the only thing that i noticed is the occasional crash if i work with smart art (though wine page says it doesn't work it is not explain what does not work in smart art).

i've noticed some people having problems. either on wine upgrades/updates or similar. and then being advised to dual boot or use windows.

but what about using office in virtual box (winXP+ms office 2007)? would it take too much resources? how fast does it all run on modern maschines (specifically i3 1.8Ghz or A4 2,5Ghz CPU with 4 GB ram). My only brush with vbox is on my signle core maschine with 2GB ram running winxp with Xubuntu as guest. and it is not that fast once i open a few programmes. and the E-450 can also run some light OS (e.g. Lubutnu) in vbox reasonably well i've found.

which option is better for casual computer user? wine or open office? dualboot is too tedious just to use the office. and i don't want to explain the magic behind how it all works too much.

Libre office is not really an option in this case (compatibility etc.). Though i might still convince them to use it later on.