Which Reference Management Software do you use? (Reader Poll)

When I started grad school I started using Reference Manager (RefMan), similar to EndNote, to manage my references and bibliographies. It's a real pain, and I often feel like I'm powering my computer with the endless pumping and clicking of the mouse that it takes to import a reference into my library.

Recently I've started using Zotero because of how easy it is to import references, store PDFs, and sync between computers. It also integrates with MS Word and allows you to insert citations and format a bibliography using any of EndNote's styles. And it's free.

Before I make the switch and leave RefMan for good, I would love to see what everyone else here uses to manage references. I know many of you use social bookmarking sites like CiteULike, del.icio.us, FriendFeed and others to save and share literature, but I'm really interested to see what software you use while writing to manage references and format bibliographies, and how satisfied you are with what you use.

Thanks for responding! Check back in a few days and I'll summarize what you all said.