The flexible accordion tube things you mean?They are a clog waiting to happen.
No they are not any good. Although it takes more thought, there is always a way to hook up the trap without using any accordian style fittings. They are prone to clogs and failure resulting in damaging leaks.Are the accordion like P-traps any good? I worry about stuff getting stuck.
Would this kind be ok (obviously it would have a different shape to hook to the soil pipe).
I don't know if the accordion style things are any good.