I have dealt with a lot of lead sheathed cables in homes in the UK. It was used extensively until the advent of rubber sheathed and pvc sheathed came along. As you guys have all said, it is a pig to ground properly, you have to have skill and patience to ensure a good connection. Even then, with time they loosen and become ineffective - best to get rid I say, yup, they have had their day.
We do still have a lot of underground lead sheathed service cables though, the same grounding issues arise here. Only recently I had to check out the grounding on someone's home and found it totally useless due to a crack in the service cable lead sheath. The Utility company arrived PDQ when I pointed out this!
