i upgraded my lab from 220.127.116.11.
-FirePower Services on asa5508
-Virtual FTD with fdm
all works fine. Now issues during upgrade. Love it
Don't upgrade to it yet. Go to 18.104.22.168 and stay at that version until Cisco gets the bugs fixed in 6.3. I've opened 3 cases since I upgraded to 6.3 and all issues were traced back to a bug or being investigated by the BU as a potential bug. I spoke to a senior engineer on the FirePower team and he said 22.214.171.124 is the most reliable version right now even though they have 126.96.36.199 out now.
6.3 is fine. Upgrade went great. 188.8.131.52 to 6.3.
Read the documentation, know what you're doing, be patient, pay attention to appliance health during the procedure. Four 5545X ASA's on 9.6 with FP Services, FMC virtual on b series blades.