Upgrading from R5.0.12 to R6.0.3 or R6.5?

Well folks, it’s about time for me to upgrade my Notes infrastructure at work. We are currently on Domino 5.0.12 and I want to move to either 6.0.3 or 6.5. The question I have for all of you is, who has been through this upgrade and has there been a lot of pain involved?

The good thing for me (as far as the upgrade is concerned) is that I am only really running web apps on the servers.  No mail, and very little RPC. So, even though the upgrade may wreak havoc with mail, that’s not a lot of concern for me.  Also, I will upgrade my hub, and two app servers, but I want to keep my Sametime server running on R5 to avoid problems.  I am using Notes intranet password authentication for Sametime, so will the address book changes hurt me there?I do have the Redbook for Upgrading to Notes and Domino 6. It seems straightforward enough, but I wonder if there are any gotcha’s with 6.5???  Can any of you other gurus shed any light on the topic, or should I just take the plunge?