hi, I got few thoughts which can help you.
1) did you check the latency in the replication monitor.
2) did you check the database properties for auto update indexes and statistics,
3) and Analyse the purpose of the replication over mirroring in your case.
I have setup transactional replication between two sql 2008 instances and it is very slow in replicating.
We have some jobs that add thousands of records at the publisher and these take a very long time to reach the subscriber. It is not the whole database that is replicated, just a few articles but they are chunky tables. Also one table is consistently added to throughout the day, this is also not replicating well.
Are they any alternatives i could use that will help? (i.e. mirroring?)