Everyone on this forum has been in the situation, where they have inserted a game to play and they have been met with an update screen, you have to chose to either cancel the update or sit their waiting on an update screen for the update to be downloaded, well it seems that has changed now, for PS Plus users at least, pressing the circle button no longer cancels the update, but instead downloads the file in the background, here is a quote from the source:

One feature PS3 gamers have often lobbied for is the ability to download game patches, which can often be large files, in the background while still using the system to play or watch other content. However, by manipulating the PlayStation Plus Automatic Update feature you can now download game patches in the background, and new system information screens displayed during the process suggest this is a planned feature which may be officially implemented in a future firmware update.

For a full guide on how to do this process, visit the source on the link below:

Blog: PS3 game patches can be downloaded in the background