Server Administration :: Enable Row Movement?

I have a job that runs the following commands for each table in a schema.. (I just inherited it ugggg)

alter table ODS.ODS_MONTHLY_MF_AUM enable row movement;
alter table ODS.ODS_MONTHLY_MF_AUM shrink space;
alter table ODS.ODS_MONTHLY_MF_AUM disable row movement;

On occassion I get this error when enabling row movement

ERROR at line 1:
ORA-00054: resource busy and acquire with NOWAIT specified

Other than dealing with apps that depend on ROWID's is there any negative impact to always keeping row movement enabled for tables.

Secondly, does any body have a script that can determine if the space really needs to be shrunk for a table.