Change of behaviour is causing a problem - SP2 introduces a (Select All) option for multi-value parameters which cannot be switched off; this is useless without an option to turn it off.
Essentially select three options from the list eg. 1,3,4 passes that CSV through to the stored procedure and we can easily sort that into a set; we can put our own option for 'Show All' and in code determine this and for dynamic searches we can just exclude that filter clause.
Now we have a situation where we have the system generated (Select ALL) option and our own user (Show All), the former (sys gen) one forces all items to be checked which means a big CSV passed into the stored procedure which forces you to filter by that column on a dynamic search which is totally and utterly useless and inhibits performance.
We need an option to switch this (Select All) off, if its just in RDL then it needs to be exposed clearly through the GUI.