Use of Metamagic feats is one of the best features of Sorcerers. Obviously, spontaneous casting exploits MM far better than preparation. Increased casting time is a trivial penalty which most of the time is negligible (of course, sometimes is not...).
Compared to the Wizard's use of MM, the Sorcerer makes great use of the MM feats which are situation-critical (Still Spell, Silent Spell, Energy Substitution), while Wizards tend to use much more strictly enhancing feats (Extend Spell, Empower Spell, Widen Spell) which you know they are almost always going to be worth, and use the situation-critical mostly on scrolls.
I think there was a sage advice long ago, if it wasn't withdrawn later, that suggested the DMs to feel free to let Sorcerers use Quickened Spell. I think it was a good idea, since the +4 level increase is such an expensive cost already that justifies the benefit. A Sorcerer who uses QS to cast 2 spells/round is going to deplete her higher spell slots very quickly (remember that Sorcs are always 1 spell level behind the Wizzies, although they have more slots to use), which could be a good choice sometimes but not always.