I've been an OpenOffice.org user ever since I first installed Ubuntu in 2008 (now a Debian unstable user). I just tried installing AbiWord and Gnumeric, and compared the startup times of AbiWord and OpenOffice.org Writer, on Debian sid with Xfce.
AbiWord: 3 seconds
OpenOffice.org Writer: 12 seconds!!!
As soon as I found that difference, I decided to use AbiWord and Gnumeric in place of their OpenOffice.org counterparts - although I've left Impress installed because as far as I know, there is no GNOME Office equivalent.