I built a homemade Amiga 9pin to USB adapter with the help of a few people over at EAB. Very easy to do and works a treat in WinUAE using Vista.
Here is a thread I made with a few pictures.
http://eab.abime.net/showthread.php?p=479779#post479779The adapter works very well, supporting 2 independant fire buttons and could do autofire but I chose not to due to laziness.
No lag with this crude but very effective adapter.