1.5 (1.45 ,.46 and builds in between).

• Full Ultrapeer and leaf modes
• Vastly improved searching and connectivity.
• Metadata search ( not accessible yet in beta, but completed).
• GGEP support implemented.
• Search Panel updated.
• Webcache list auto-update implemented.
• Askjeeves search added.
• Various bugs and errors addressed.

Version 1.56 ( there were many build in between, 1.56 is the public version since 1.5).

• better control the bandwidth usage in network options
• Automatic throttling control added for query flood prevention
• improved search horizon
• All around performance and efficiency improvement based on weeks of internal testing 1.5* builds and feedback from fellow Gnutella developers

it is highly recommended you update to this latest version