well there are alternatives to Microsoft office.. open office is one of them...
plus if u need to use quickbooks,m pretty sure u can run ur windows applications through Wine... i am not sure whether Wine comes pre-installed in ubuntu or not but u can download it and run windows application through it..
m using backtrack 5 which comes with Wine and i used it to run very very old application Digital works to build circuits.. u shud give it a try!! if problem post here again! lol