In seven years and three cars (2003 745i, 2006 650i and 2010 650i) I've never had a problem upgrading software. I've only seen improvements. All of these cars have had at least 2 software upgrades and the most was the 745 at around eight or nine upgrades. I can only tell you don't fear the upgrade and find any excuse to do it.
2012 650i xDrive|Vermillion Red Metallic | Cinnamon Brown Nappa Leather | Fine Line Oak Wood Trim | ARS | 20" Wheels | Active Cruise Control | HUD | Night Vision | LED Lights | Heated seats | Heated Steering Wheel | Ski bag | Active front seats | Premium hi-fi system | Satellite radio | Plus more
Former ride 2010 Deep Sea Blue 650i