Overall my largets DB is around 30GB (Transactionally) with one of the tables over 8GB on it'd own, it really depends on the overall Transactions.

Only had a couple of Problems when Timeouts had occurred and this stops replication when it is trying to apply a command IE Delete when the operation ahs already occurred. usually just a case of removing the commands for that article and then redoing the original steps and letting replication start over again.

Overall my I/O's todate for the Subscriber/Source Database is presently over 2TB(yes 2000 GB of I/O's)