Here, on the test systems, and one production system, the inplace-upgrade to FT SE (V5) went fine, with no problems.
I have just this week identified a bug somewhere in 5.0 relating to VBA though, so you might want to think about it if VBA is important to you. The bug I've found, is that from 2.x through 4.x, you could reliably and easily call public subs from one display to another.
With 5.x, calling a sub with no parameters works, but calling a sub that takes a parameter will almost 100% of the time, result in the parameter being read as null or nothing or empty. It seems to be a timing problem, somewhere, as if you step through the routines in a debugger, this hasn't happenned.
I'm looking currently into replacing the SE Display's that do this, with forms based off of the current window, but that won't help me in all cases.
I don't know if Rockwell has any info on this yet, and honestly, I don't feel like trying to deal with them on the support line today, or this week.