This would be really handy. Took me three years to find there was an expanded search. It could be as simple as ADVANCED SEARCH link sitting under the constantly used Quick Search box.
Search will also drag more of those noobs in. Convert the casual searcher into a contributor.
Yeah, yeah, I know the menu option shouts SEARCH but amazing what the brain fails to see every day when it has been taught that search is in the corner.
As an editor, things I use a lot on the front page are:
*My Data menu (everything)
*My Profile menu
*Quick Search box
*Blog news list
Talking of the top menu. It seems strange that About Us\Products are next to Editing\Search\Documentation. The first pair are for those who want to know what MusicBrainz is. The other three are in constant use by editors. Seem a strange fit side by side.
Also second most of what @elomatreb just said. Make the forum more findable as it is so helpful, friendly and plain darn useful. The site and Picard can be confusing to noobs and they need the forum.
It is also worth thinking of your slightly different groups. I came here as a tagger, stayed as a database editor. I doubt I am unique in that. Picard and Tagging drew me in. They need to be loud and prominent. That is how you get the noobs addicted