Go-oo has built in OpenXML import filters and it will import your Microsoft Works files. Compared with up-stream OO.o, it has better Microsoft binary file support (with eg. fields support), and it will import WordPerfect graphics beautifully. If you are reliant on Excel VBA macros - then Go-oo offers the best macro fidelity too. If you expect your spreadsheets to calculate compatibly, or you get embedded Visio diagrams in your documents, you'll want Go-oo.
Go-oo's user interface is more familiar, with lots of small pieces of polish. We have built-in (working) multimedia integration on Linux, a beautiful solver component, and your Chinese should look sane. We also integrate with your system better by default: eg. enabling native file-selectors on Linux.
From first-time startup, where we sort I/O to reduce seek cost, to a highly optimised second start application and a systray quick-starter on Linux we are faster. We use less memory than up-stream, we link faster, use better system allocators, and don't waste so much time & memory in the registry. Go-oo performance is hard to beat.
Contributing code to go-oo is simple, and fast, following the traditional hackers' process of peer code review: just mail patches to the mailing list, or when we get used to your code - commit your patch immediately to HEAD ooo-build: no CWS, no hours of tagging, paperwork, no specification, no hassle. Of course - if your patch sucks - expect to hear how it can be improved.
For the code to live, grow and improve, to encourage participation and compete with the other office suite - we need sensible licensing: ie. weak copy-left. While in general we think LGPLv3 is a great & sufficient license for our code, others eg. Sun & IBM appear reluctant to include LGPL code into their products, and prefer other licenses such as the CDDL (a weak copy-left derived from Mozilla's MPL). Luckily dual licensing under the LGPLv3 / CDDL can help here - and we recommend this for the majority of our code.
We believe that copyright assignment to a single corporate entity opens the door for substantial abuse of the best-interests of the codebase and developer community. As such, we prefer either eclectic ownership (cf. Mozilla, GNOME, KDE, Linux), or an independent, meritocratic foundation (cf. Eclipse, Apache) to own the rights. Having said that we recognise and applaud Sun's technical contribution to OpenOffice and recommend that small patches & fixes to existing Sun code should be assigned to them under the SCA, and up-streamed.
Go-oo is a developer run meritocracy. If you want to contribute something concrete: code, bug fixes, bug triage, significant translation, build-bot maintainance etc. then there is a place for you as a key part of the team. If instead, you want to market Go-oo, install it, talk about it - that's really excellent, but this is not our focus: there are no formal roles in development to reflect this valuable work.