I installed V5. My desktop icon for version 4.1.2 disappeared. The program is still there, but I had to dig around and create a new icon. Annoying, but not fatal.
The first thing I needed to do was change filament. I got the machine control program talking to my printer, fired up the hotend, and then told it to retract the filament. I expected it to import ALL of my old settings. Instead of the setting of 70 mm/min I have used for years, it ran it at 240 mm/min, and yanked the molten filament out thru my extruder before it had a chance to cool. My extruder is now coated internally with smears of molten filament, and I will have to tear it apart to clean everything. That pretty much kills my evening.
Thanks loads guys...