SMP is highly unstable with multiple users on. Tick will jump wildly depending on the activities other users are doing.

Being in the same chunk as a village is almost impossible as the lag spikes through the roof. 300+ tick is not uncommon. Other activites I'm yet to discover are causing these issues. Never experienced any of this in 1.5.2.

And just for reference, had 300+ tick in 1.5.2 when a user built a village breeder and there were over 180 villagers. Same lag in 1.6.1 just from simply ENTERING a village chunk(not same one with 180).