thanks for replying guys!

Mr(?) Noob, your way certainly gets round the upgrade problem.

Trouble is I am greedy and was really hoping to leverage SRDF to keep the failover in synch for me by replicating system databases as well. Because there are not just logins, but DTS\SSIS, agent jobs, linked servers as well. If they could just be kept in synch and just be there when we failover that would be so good and justify SRDF as more than a faster way to failover and back. Quite keen that the failover server ends up with the same name as the primary as well.

Michael, I like the boot from SAN idea, do you do that?. Our intel guys don't seem keen, saying there are performance problems. Seems to me it would give the slickest failover though.

I will be setting up a proof of concept and try all options I can think of, see how they compare.

Other option appears to be replicate system databases but not C, and split the disks being replicated when we do upgrades then re-establish SRDF.