I had a discussion with the service manager at my dealership today and asked him if they have been getting owners complaining that the update caused the Spyder to run worse. He said that they personally haven't been getting complaints but he's seen the online talk of Spyders not running right after the update. He told me he thought it was an issue with the dealership doing the update correctly. There is more to be done above plugging into BUDS, accepting a few questions or prompts in a text box, and then unplugging the Spyder. Like widowmaker2011 stated in a previous post, there are other components that need to be reset or re-zeroed (like the TPS) for everything to work right. If the tech misses those steps, the computer is now using invalid data about throttle position, steering angle, yaw, etc. when trying to determine how much fuel to give to the engine or whether the VSS needs to intervene.
Probably those that have had a great running Spyder since doing the update had a tech who did the update 100% correctly. Those who've had issues probably had a tech that didn't pay attention to the full update instructions so they don't know that there is more to the update (but they think they know and think they did it correctly).