The initial version is great, but there are some small-but-crucial things missing;
Indicate who invited you on the Workspace Invite email
The "You've been invited" email does not indicate who invited you, so you have no idea which clients are confirmed. Please add that.
Allow us to remove ourselves from 3rd party Workspaces
Once in a workspace there is no obvious way to remove yourself from that workspace, which means huge clutter issues.
Allow the workspace owner to invite to specific projects only
There is no way to limit access to an individual project. In 90% of cases, a client wants help with one project, but cannot invite me to the workspace due to NDA's they have on other client projects.
Allow workspace name customization by the invitee
Workspace names are often nonsensical, and don't actually identify the client clearly. Sometimes it's very difficult to guess which client is which workspace.