Just today I replaced my wash machine hoses with the new high pressure, high burst pressure hoses. I did this for maintenance reasons, as the old standard hoses were 10+ years old and I felt they were overdue for a change. Our washer is on the first floor.
Well, now I have water hammer (big time) that I didn't have before. The new hoses are so stiff, they don't absorb the pressure pulses that occurs when the solenoids suddenly close. I solved this new problem temporarily by closing down the valves that feed the wash machine, but it looks like I'll be installing some water hammer arrestors in the near future.
There is always something!