I'm kind of split on this issue. On the one hand, security against malicious attacks is obviously a good thing. The harder it is for some random app or even website (via a suitable browser/plugin exploit) to steal your data, the better.
The trouble is that most manufacturers and network providers treat the user as an enemy to protect the precious phone against, so they do everything they can to prevent users from doing anything that makes them less likely to quickly buy a new phone (such as installing 3rd party updates like CyanogenMod). This gives them even more power in this regard.