Stief sent me this info.:

The easiest way is to look at the connections page: it should say Ultrapeer (leaf) in the space above the connections list

The second way in in the bug reports

Detail: Example

-- listing session information --
Current thread: AWT-EventQueue-0
Active Threads: 140
Uptime: 1:14:09:07
Is Connected: true
Number of Ultrapeer -> Ultrapeer Connections: 32
Number of Ultrapeer -> Leaf Connections: 29
Number of Leaf -> Ultrapeer Connections: 0
Number of Old Connections: 0
Acting as Ultrapeer: true
Acting as Shielded Leaf: false