I have 1 BCM50 in my inventory. It is at a remote office with 2 users, and has worked like a champ for about 2 years with no service issues. I have 12 channels off a PRI for trunking, and am very happy with the system's performance.
I have not had to install any additional patches since the initial install. I know I am behind on patches, but the system is running clean, and this office is kind of in a remote area, so I don't get to visit it often.
The rest of my inventory consists of 9 networked CS1000's (5 CS1000e's, 3 CS1000s's, and 1 CS1000M cabinet) and 10 other BCMs (a combination of 1000's, 400's, and 1 200) running software from 3.6 to 4.0.