There is no such thing as "excellent Microsoft Office compatibility", Microsoft has insured that by changing document formats often and documenting them rarely. Hell, even Office itself fails loading older Office files correctly.

But, as long as you are comfortable with "decent Microsoft Office compatibility", any company that is making office suites for Symbian/S60 (there are three or four) can be persuaded to port its stuff to Maemo, for a reasonable fee. I am guessing the "reasonable" figure from the assumption that they are not making fortunes selling office suites for 240x320 mobile phones.