"Thumbs up" to the above good advice!
Yes, replication will work if one server is running SQL Server 2008 SP2 and the other is on SQL Server 2008 R2 SP1. (The important thing is that both SEPMs have the same exact version of SEP running). Personally, I recommend ensuring that all MS SQL servers are always updated to their latest SP and patch level. Also ensure that those MS SQL servers have regular backups and maintenence tasks running, and that an admin is checking their logs to ensure that the servers are healthy and performing well.
That is all just MS SQL best practice. If the MS SQL servers crash, run into difficulty or are compromised, it can have a serious effect on the SEPMs! A ittle upkeep and prevention is far better than a crisis. &: )
With thanks and best regards,
Mick