OpenOffice.org is a great piece of open-source software, but there's no denying it's more than a bit bulky and sluggish. There's no need to worry, though, since there's a fork of the source code called Go-OO that picks up most of OpenOffice's slack.
Go-OO sports an enhanced interface and is much easier to use, with larger icons and less clutter. It still sports drop-down menus for fast customization, but there's no doubt that Go-OO comes with a cleaner layout. It also comes with an importer to handle DOCX, XLSX, and PPTX formats, and natively supports SVG files. Graphics rendering is greatly improved, too, including VBA support, Mono integration, better display of Chinese characters, support for WordPerfect graphics, and EMF rendering.
OpenOffice must be uninstalled before Go-OO is loaded, but that's a minor annoyance. Whereas Flock, for example, is a Firefox fork geared for a particular kind of user, Go-OO should appeal to anybody who loves OpenOffice but is looking for something that's leaner--but hardly meaner.