There's a long list of new features for the 3.3 release, but a couple stand out above the rest for me.
Top of the list? Bundling the presenter mode extension with Impress. This lets the presenter see the current and next slides, along with a clock to see how much time has passed in the presentation. Having used Impress for dozens of presentations, I'm very pleased to see this making the mainstream release. (Here's hoping Impress will gain some of the same collaboration features that Writer has now.) Now I just need to give a few presentations to test it out...
Another nifty addition? "Experimental" mode — which allows more adventurous users to try out unfinished features. Well, I suppose less adventurous users could as well. At any rate, I like having the option to try features that are works in progress if I choose. This may go well with the time-based releases that are planned for LibreOffice.
Speaking of time-based releases, the LibreOffice release plan and development process being developed around LibreOffice is definitely in the top five. Granted, this is something 99% of LibreOffice users won't really come into contact with directly — but it's what will make LibreOffice successful in the long run. OpenOffice.org development has really stagnated in recent years due to Sun's poor governance of the project. Having a true community development process means that more developers are likely to be involved and contributing features. The time-based release schedule will help keep LibreOffice evolving at a good clip.
LibreOffice 3.3 brings SVG import for Writer and SVG editing in Draw — important because many projects distribute logos, etc., as SVG. It's nice to be able to include graphics in their native formats rather than having to convert to PNG or whatnot and then use the images.
Finally, PDF import. LibreOffice adds the ability to import (and edit) a PDF in LibreOffice Draw. Since the 3.3 release I've tried it out on about a dozen PDFs and it works really well. It could use some improvement on text-heavy documents, but if you need to make a few minor changes to a PDF it could be very useful. For instance, I have a few old presentations that I've saved as PDF and have since misplaced the original Impress files. This way I can easily make minor changes to the slides and reuse.
For all the improvements in the 3.3 release, though, it's not a huge leap from OpenOffice.org. Keep watching — I suspect that the next few releases of LibreOffice are going to be very interesting.