I use it and endorse it heartily.
I still have Micros|_|ck Office installed (my $200 used laptop came with it installed; I would never ever let one penny of mine end up in Micros|_|ck's pockets) for survivalism's sake; but OpenOffice has taken excellent care of me.
There's a very gentle learning curve, as many of the menus and keyboard shortcuts are the same ones you'd find in Office.
The macro facility is far superior to VBA; you can write macros in OpenOffice Basic (which again has a low learning curve if you're VBA-conversant), and the super thing is, there are API's so you can also use other languages like Python to interact directly with your OOo documents.
OpenOffice.org kicks ass.
Edit: One frustrating thing is that Base, the database applimacation, doesn't support an ODBC driver; and ODBC is the only way I know how to pull data straight out of databases into my BASIC programs. So I've had to install MySQL and use it as my database server of choice, using SQL functions in my OpenOffice programs to interact with it. I still haven't figured out how to make this JDBC thingy work...

[Edited 2011-01-14 03:24:31]
Pancakes are delicious.