I used several Male/Female Bullet connectors throughout my underdash wiring. I had seen them illustrated and thought they were a viable option to be able to have the ability to disconnect a circuit if necessary. I did not want to use the crimp on male/female spade connectors as they seemed bulky and I'm not a fan of crimp only connectors. Some circuits are single wire connections with shrink tubing over the actual connectors. I suggest soldering and shrink tubing at every terminal regardless of its design. On circuits that were to have common sources I used a small block of aluminum 3/16 X 5/8 x 1" long with 2 holes drilled length wise and then was able to plug 4 bullet connectors into it (2 in each end) and cover the entire block and protruding wire ends with shrink tubing. I looked at various options and this basic design was used on British cars and has worked well. Afterward I found the OEM (British) parts available through Moss Motors.
http://mossmotors.com/Shop/ViewProdu...dexID=28931#20
The entire rewiring project has had no problems or issues, it was actually sort of enjoyable at the time.