Gee .. this thread just lives forever dosent it.. !
no, valves dont leak.. (unless they're not installed correctly in the first place!).. i do a lot of work for subsea valve manufacturers who do the valves for BHP and Rio, and when i first got my Fumoto i took it and showed them.. they pulled it apart and said it was excellent, then they bought some as well..
http://www.fumoto.com.au/ is the main site for them.. there is a lot of information on there about the build quality and robustness of these units.. have a read.. they are really a good product.. Ive had mine on now for over 3 years and never had a problem.. it makes it a lot easier to drain oil with the TJM bash plates on too.. all i have to do is push the drain hose that i use on the fumoto and turn the lever.. (yes you still have to convolute your hand on strange angles), but it still is easier.. and you dont get oil all over the inside of the bash plates etc..
Cheers
Steve