I am an unabashed fan of Gerrit - the fine-grained ACLs can be annoying to wrap your head around, but the code review interface is quite nice.

the only thing I've found missing is the ability to render images inline. If someone submits a documentation update with SVG and PNG updates, you have to download the changeset to see the files. It would be nice if an option for "view this attachment inline" were available without installing extensions.