I use NeoOffice periodically. Its not that bad, really. Its pretty much a clone of Microsoft Office XP/2003, so its not really all that Mac-like, but its Word and Excel compatibility is very, very good - much better than Pages/Numbers, Nisus Writer, Mellel, etc. Haven't really used NeoOffice's presentation module, so can't speak to its compatibility.
Takes a little bit to launch the first time, but big deal... not like it should be a deal-breaker.
The developers are very good about patching/upgrading the application on a regular basis. About I year ago I donated money to the project to help continue its development.
While its not as "Mac-like" as Office 2008, it may actually have fewer bugs than Office 2008 in its current state. For example, it actually works properly with Exposé and Spaces.
And there are separate optimized builds for PPC Macs and Intel Macs.