NeoOffice is a Java based port of Open Office for OS X. The generic version of Open Office on OS X uses X11. I find that NeoOffice, being OS X native, is a lot less clunky. Even so NeoOffice is still rather sluggish, especially on my poor likkle G3. Goodnews however! NeoOffice for Intel macs is almost ready. Either way I certainly recommend it for OS X users.
Meantime here's a link to the latest Alpha 3 version of NeoOffice 2.0: NeoOffice Download for PowerPC