I have two production installations of V5 on the SG20. Small buisness installations. Other than the current POP3 proxy problems, it appears to work fine. Getting V5 on the SG20 is a bit of a hurdle though. Let me know if you want my notes on the process.
No, my LCDs don't work. I think there is an post somewhere on the forum that describes a hack with v4 information to get it to work.