Is there a GUI utility to mount remote filesystems over SSH?

It's not clear to me if you are strictly bound to using sshfs, but by default the GVFS in GNOME supports SSH connections. In the file manager go to File -> Connect to server:

This will mount the remote SSH server in a folder you can access from the file manager. If you need to access the mount in the command line it's in .gvfs.

You can also mount it in Nautilus. Just hit CTRL+L and in the address bar type: ssh://server-ip/somepath/

• Where is "Connect to Server" for ssh connections in Unity?

Another option is Gigolo:

(Click above to install).

If you just need to access the remote filesystem, you should be able to go to sftp://hostname.example.com in your file browser without having to mount it.