I am looking for a decent online project management software with Gantt charts. I tried several online project management software, some free, some partially free with paid upgrades like BaseCamp, Zoho etc.

The free online project management software I tested are: phpprojekt (self-hosting), phpCollab (self-hosting), Basecamp (hosted only), Zoho (hosted only) and dotProject.

Some like dotProject supports Gantt chart but using it is clumsy and Web 1.0 UI (no live updating, doesn't feel like using Microsoft Project or GanttProject).

Basecamp doesn't think Gantt chart is useful and refuses to support it. It just looked to me like a collaborative Notes and To-Do list, not a project management tool. I heard many good things about Basecamp, I am unimpressed.

Zoho is light-weight Bascamp, another collaborative note-taking application and to-do list.
BTW: Zoho's spreadsheet is pretty good.

Do you know any decent online project management software which can be used as a replacement for Microsoft project or GanttProject?

For now I am sticking with GanttProject, which is free and works very much like MS-Project and with the ability to share documents over ftp and Web-DAV.