Tuning indexes on tables associated with replication can be a bit fun. You do need to make sure that the indexes you have in place for queries are necessary as that of course is more costly on replicated inserts, updates, deletes. Depending on the nature of the data and the change rate you may find that you need to rebuild them more often than other indexes so, do some monitoring on the fragmentation. Additionally, you should certainly consider updating statistics on those tables / indexes more frequently if you determine that you can't rebuild the indexes on a more regular basis.
David
@SQLTentmaker
“He is no fool who gives what he cannot keep to gain that which he cannot lose” - Jim Elliot