I just installed Crossover Office 5.0 from Code Weavers. I successfully installed and am running Microsoft Office 2003. The embedded help works great. Crossover Office costs $40 from codeweavers.com. Installing the Crossover Office was simple. Then installing MS Office 2003 into Crossover Office was almost as simple. It automatically added entries into my KDE application menu for itself and for the MS Office applications. Easy as can be.
I have also recently installed and am running Open Office 2.0.1. It is running great as well. It can open genuine Excel files with no problems. I haven't tested the word processor on genuine MS Word document files yet. I am using the OOo word processor to create business cards. It's taking a little time to get used to it. I've never been much of an office suite guru. So far the business card project looks promising.
Let's not forget about other excellent FOSS office applications. I have a very high regard for Koffice and for Abiword and Gnumeric.