Performance problems are being reported that can be resolved by updating the cardinality statistics used by the optimizer. Currently the only time the statistics are guaranteed to be an up-to-date is when the index is first created on a fully populated table. This is most easily accomplished on an existing table by using the command:
alter table <table-name> compress [sequential]
Compress table is an I/O intensive task. A better way to achieve this would be to re-enable parser support for the 'update statistics' command or re-implement the update in some other fashion.