table-statistics

What are the implications of having out of date table statistics on a Sybase/SQLServer database?

For example, for heavily used tables with volumes in the order of 10 million rows that grow by a million rows a month, if the stats are 6-8 months old how detrimental to the performance of the database is this going to be? How often should you be refreshing the stats? ...

Do table statistics get updated during the creation of a clustered index?

After I have created a clustered index on a table, is there any point in updating the statistics for that table? Cheers. ...