Fit and finish differ somewhat between the two suites, with icons and other assets swapped out, though they're sized and positioned exactly the same on both. Overall, I thought OpenOffice.org's icons were a little easier for new users to understand, but of course that's all subjective; really, it's a wash.
I had expected Microsoft Office compatibility to be a major area of competition between the two suites, but alas, not much work seems to have been done there. Both suites handle files from Office 2003 and earlier reasonably well, but support for the newer, XML-based file formats is poor for anything but simple documents. XML-based Excel workbooks survive the transition the best, but migrating .docx and .pptx files is sure to be arduous. If anything, OpenOffice.org was slightly more faithful to Word font styles in some test cases, but overall presentation was so lousy it hardly bears mentioning.
If you're familiar with OpenOffice.org, you'll be right at home in LibreOffice.
Even the old-format Office files aren't fully supported. Only a portion of PowerPoint's transitions and text effects are available, although the ones that aren't tend to degrade gracefully. How Writer handles complex Word documents can be unpredictable, to say the least, particularly when it comes to fonts. Calc has done an admirable job of supporting basic Excel macros, but not all capabilities are available there either (and it might be unreasonable to expect full compatibility). Unfortunately, LibreOffice does not appear to have done much of anything to improve on OpenOffice.org in these areas.
Still, the similarity between the two suites is overwhelmingly positive when you consider that LibreOffice announced its first stable release in late January. I found no difference between the two offerings either in performance or stability. Neither crashed on me, even when handling documents designed to put productivity apps through the wringer.
New features in LibreOffice What LibreOffice does bring to the table are mostly small, incremental improvements to the functionality of OpenOffice.org. For example, LibreOffice Calc ships with a new set of default key bindings that should be more familiar to users accustomed to Excel or other spreadsheets. Writer includes a new dialog box that makes it easier to format document title pages. And while Microsoft Office support hasn't much improved, LibreOffice does a better job than OpenOffice.org at handling Microsoft Works, Lotus Word Pro, and WordPerfect documents. Various bugs have been fixed, as well.