I've been playing with the latest OpenOffice(which has just gone to 1.0) and I must say that it is pretty darn good, giving me no problem with common documents, both .doc and .xls files. Yes, it is a hefty program, weighing in at about 60MB, but it works pretty well.

You can download it from the main site or there are debian binaries available by putting the following in your /etc/apt/sources.list:

deb http://apt-proxy.sf.net/openoffice unstable main contrib

and then doing "apt-get install openoffice.org". Kudos to the OpenOffice team.